| 1. |
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| 2. |
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| 3. |
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| 4. |
- Löfberg, H, et al.
(författare)
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gamma-trace in human pituitary adenomas
- 1984
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Ingår i: The Journal of clinical endocrinology and metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 59:1, s. 8-113
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Tidskriftsartikel (refereegranskat)abstract
- gamma-Trace, a small protein occurring in body fluids and in secretory and neuroendocrine cells, was demonstrated by immunohistochemical techniques in the cytoplasm of the tumor cells of 13 pituitary adenomas obtained at surgery and autopsy. Seven of the adenomas also contained LH immunoreactivity. FSH, TSH, and ACTH were each found in one gamma-trace-containing adenoma. gamma-Trace was also demonstrated in extracts of 1 pituitary adenoma and of 5 nontumorous adenohypophyses. The immunoreactive protein found in the extracts had a molecular weight and electrophoretic mobility characteristic of gamma-trace. Computerized amino acid sequence comparisons between the primary structure of gamma-trace and those of known hormonal peptides showed no significant similarities.
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| 5. |
- Roblick, U J, et al.
(författare)
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Sequential proteome alterations during genesis and progression of colon cancer.
- 2004
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Ingår i: Cellular and Molecular Life Sciences (CMLS). - : Springer Science and Business Media LLC. - 1420-682X .- 1420-9071. ; 61:10
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Tidskriftsartikel (refereegranskat)abstract
- Changes in the proteome of colon mucosal cells accompany the transition from normal mucosa via adenoma and invasive cancer to metastatic disease. Samples from 15 patients with sporadic sigmoid cancers were analyzed. Proteins were separated by two-dimensional gel electrophoresis. Relative differences in expression levels between normal tissue, adenoma, carcinoma and metastasis were evaluated in both intra- and inter-patient comparisons. Up- and down-regulated proteins (> twofold) during development to cancer or metastasis were excised and submitted to peptide mass fingerprinting and MS/MS sequence analysis, facilitated by the use of a compact disc workstation. In total, 112 protein spots were found to be differentially regulated, of which 72 were determined as to protein identity, 46 being up-regulated toward the progression of cancer, and 26 down-regulated. Several of the identifications correlate with proteins of the cell cycle, cytoskeleton or metabolic pathways. The pattern changes now identified have the potential for design of marker panels for assistance in diagnostics and therapeutic strategies in colorectal cancer.
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| 6. |
- Benach, J, et al.
(författare)
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Structure of bacterial 3 beta/17 beta-hydroxysteroid dehydrogenase at 1.2 angstrom resolution : A model for multiple steroid recognition
- 2002
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 41:50, s. 14659-14668
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Tidskriftsartikel (refereegranskat)abstract
- The enzyme 3beta/17beta-hydroxysteroid dehydrogenase (3beta/17beta-HSD) is a steroid-inducible component of the Gram-negative bacterium Conramonas testosteroni. It catalyzes the reversible reduction/ dehydrogenation of the oxo/beta-hydroxy groups at positions 3 and 17 of steroid compounds, including hormones and isobile acids. Crystallographic analysis at 1.2 Angstrom resolution reveals the enzyme to have nearly identical subunits that form a tetramer with 222 symmetry. This is one of the largest oligomeric structures refined at this resolution. The subunit consists of a monomer with a single-domain structure built around a seven-stranded beta-sheet flanked by six alpha-helices. The active site contains a Ser-Tyr-Lys triad, typical for short-chain dehydrogenases/reductases (SDR). Despite their highly diverse substrate specificities, SDR members show a close to identical folding pattern architectures and a common catalytic mechanism. In contrast to other SDR apostructures determined, the substrate binding loop is well-defined. Analysis of structure-activity relationships of catalytic cleft residues, docking analysis of substrates and inhibitors, and accessible surface analysis explains how 3beta/17beta-HSD accommodates steroid substrates of different conformations.
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| 7. |
- Bergman, T, et al.
(författare)
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C-terminal sequence analysis
- 2003
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Ingår i: Current protocols in protein science. - : Wiley. - 1934-3663 .- 1934-3655. ; Chapter 11, s. 11.8-
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Tidskriftsartikel (refereegranskat)
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| 8. |
- Bjellerup, P, et al.
(författare)
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Limited neuropeptide Y precursor processing in unfavourable metastatic neuroblastoma tumours
- 2000
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Ingår i: British Journal of Cancer. - 0007-0920 .- 1532-1827. ; 83:2, s. 171-176
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Tidskriftsartikel (refereegranskat)abstract
- Neuropeptide Y (NPY) is found at high concentrations in neural crest-derived tumours and has been implicated as a regulatory peptide in tumour growth and differentiation. Neuroblastomas, ganglioneuromas and phaeochromocytomas with significant concentrations of NPY-like immunoreactivity were investigated for different molecular forms of NPY and for significance of proNPY processing. Gel-permeation chromatography identified intact NPY (1-36) in all tumours, whereas proNPY (69 amino acids) was detected only in control adrenal tissue and malignant neuroblastomas. Purification of NPY-like immunoreactivity in tumour extracts and structural characterization revealed that both NPY (1-36) and the truncated form NPY (3-36) was present. The degree of processing of proNPY to NPY in tumour tissue was lower in advanced neuroblastomas with regional or metastatic spread (stage 3 and 4) (n = 6), (41%, 12-100%, median, range), compared to the less aggressive stage 1, 2 and 4S tumours (n = 12), (93%, 69-100%), (P = 0.012). ProNPY processing of less than 50% was correlated with poor clinical outcome (P = 0.004). MYCN oncogene amplification was also correlated to a low degree of proNPY processing (P = 0.025). In summary, a low degree of proNPY processing was correlated to clinical advanced stage and poor outcome in neuroblastomas. ProNPY/NPY processing generated molecular forms of NPY with known differences in NPY-receptor selectivity, implicating a potential for in vivo modulation of NPY-like effects in tumour tissue. (C) 2000 Cancer Research Campaign.
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| 9. |
- Drobni, Mirva, et al.
(författare)
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A host-derived pentapeptide affecting adhesion, proliferation and local pH in Streptococcus-Actinomyces biofilm communities.
- 2006
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Ingår i: Infection and immunity.
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Forskningsöversikt (populärvet., debatt m.m.)abstract
- Salivary proline-rich proteins (PRPs) attach commensal Actinomyces and Streptococcus species to teeth. Here, gel filtration, mass spectrometry and Edman degradation were applied to show the release of a pentapeptide, RGRPQ, from PRP-1 upon proteolysis by Streptococcus gordonii. Moreover, synthetic RGRPQ and derivatives were used to investigate associated innate properties and responsible motifs. The RGRPQ peptide increased 2.5-fold the growth rate of S. gordonii via a Q-dependent sequence motif, and selectively stimulated oral colonization of this organism in a rat model in vivo. By contrast, growth of Streptococcus mutans, implicated in caries, was unaffected. While the entire RGRPQ sequence was required to block sucrose-induced pH-decrease by S. gordonii and S. mutans, the N-terminal Arg residue mediated pH-increase (i.e. ammonia production) by S. gordonii alone (which exhibits Arg catabolism to ammonia). Strains of commensal viridans streptococci exhibited PRP degradation and Arg catabolism, while cariogenic species did not. The RGRPQ peptide mediated via a differential Q-dependent sequence motif, adhesion inhibition and desorption of PRP-1-binding strains of A. naeslundii genospecies 2 (5 out of 10 strains) but not of S. gordonii (n=5). The inhibitable A. naeslundii strains alone displayed the same binding profile as S. gordonii to hybrid peptides terminating in RGRPQ or GQSPQ, derived from the middle or C-terminal segments of PRP-1. The present findings indicate the presence of a host-bacteria interaction where a host peptide released by bacterial proteolysis affects key properties in biofilm formation.
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| 10. |
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| 11. |
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| 12. |
- Filling, C, et al.
(författare)
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Critical residues for structure and catalysis in short-chain dehydrogenases/reductases
- 2002
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 277:28, s. 25677-25684
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Tidskriftsartikel (refereegranskat)abstract
- Short-chain dehydrogenases/reductases form a large, evolutionarily old family of NAD(P)(H)-dependent enzymes with over 60 genes found in the human genome. Despite low levels of sequence identity (often 10-30%), the three-dimensional structures display a highly similar alpha/beta folding pattern. We have analyzed the role of several conserved residues regarding folding, stability, steady-state kinetics, and coenzyme binding using bacterial 3beta/17beta-hydroxysteroid dehydrogenase and selected mutants. Structure determination of the wildtype enzyme at 1.2-Angstrom resolution by x-ray crystallography and docking analysis was used to interpret the biochemical data. Enzyme kinetic data from mutagenetic replacements emphasize the critical role of residues Thr-12, Asp-60, Asn-86, Asn-87, and Ala-88 in coenzyme binding and catalysis. The data also demonstrate essential interactions of Asn-111 with active site residues. A general role of its side chain interactions for maintenance of the active site configuration to build up a proton relay system is proposed. This extends the previously recognized catalytic triad of Ser-Tyr-Lys residues to form a tetrad of Asn-Ser-Tyr-Lys in the majority of characterized short-chain dehydrogenases/reductase enzymes.
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| 13. |
- Filling, C, et al.
(författare)
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Structural role of conserved Asn179 in the short-chain dehydrogenase/reductase scaffold
- 2001
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 289:3, s. 712-717
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Tidskriftsartikel (refereegranskat)abstract
- Short-chain dehydrogenases/reductases (SDR) constitute a large family of enzymes found in all forms of life. Despite a low level of sequence identity, the three-dimensional structures determined display a nearly superimposable alpha/beta folding pattern. We identified a conserved asparagine residue located within strand betaF and analyzed its role in the short-chain dehydrogenase/reductase architecture. Mutagenetic replacement of Asn179 by Ala in bacterial 3 beta /17 beta -hydroxysteroid dehydrogenase yields a folded, but enzymatically inactive enzyme, which is significantly more resistant to denaturation by guanidinium hydrochloride. Crystallographic analysis of the wild-type enzyme at 1.2-Angstrom resolution reveals a hydrogen bonding network, including a buried and well-ordered water molecule connecting strands betaE to betaF, a common feature found in 16 of 21 known three-dimensional structures of the family. Based on these results, we hypothesize that in mammalian 11 beta -hydroxysteroid dehydrogenase the essential Asn-linked glycosylation site, which corresponds to the conserved segment, displays similar structural features and has a central role to maintain the SDR scaffold.
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| 14. |
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| 15. |
- Hederstedt, Lars, et al.
(författare)
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Processing of Bacillus subtilis succinate dehydrogenase and cytochrome b-558 polypeptides
- 1987
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Ingår i: FEBS Letters. - : Wiley. - 1873-3468 .- 0014-5793. ; 213, s. 385-390
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Tidskriftsartikel (refereegranskat)abstract
- The DNA sequence of the Bacillus subtilis sdh operon coding for the two succinate dehydrogenase subunits and cytochrome b-558 (the membrane anchor protein) has recently been established. We have now determined the extent of N-terminal processing of each polypeptide by radiosequence analysis. At the same time, direct evidence for the correctness of the predicted reading frames has been obtained. The cytochrome showed a ragged N-terminus, with forms lacking one residue, and is inserted across the membrane without an N-terminal leader-peptide. Covalently bound flavin was not detectable in B. subtilis succinate dehydrogenase expressed in Escherichia coli despite normal N-terminal processing of the apoprotein. This provides an explanation to why the succinate dehydrogenase synthesized in E. coli is not functional and demonstrates that host-specific factors regulate the coenzyme attachment.
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| 16. |
- Henriksson, M., et al.
(författare)
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Separate functional features of proinsulin C-peptide
- 2005
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Ingår i: Cellular and Molecular Life Sciences (CMLS). - : Springer Science and Business Media LLC. - 1420-682X .- 1420-9071. ; 62:15, s. 1772-1778
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Tidskriftsartikel (refereegranskat)abstract
- Proinsulin C-peptide influences a number of physiological parameters in addition to its well-established role in the parent proinsulin molecule. It is of interest as a candidate for future co-replacement therapy with insulin for patients with diabetes mellitus type 1, but specific receptors have not been identified and additional correlation with functional effects is desirable. Based on comparisons of 22 mammalian proinsulin variants, we have constructed analogues for activity studies, choosing phosphorylation of mitogen-activated protein kinases (MAPKs) in Swiss 3T3 fibroblasts for functional measurements. In this manner, we find that effective phosphorylation of MAPKs is promoted by the presence of conserved glutamic acid residues at positions 3, 11 and 27 of C-peptide and by the presence of helix-promoting residues in the N-terminal segment. Previous findings have ascribed functional roles to the C-terminal pentapeptide segment, and all results combined therefore now show the importance of different segments, suggesting that C-peptide interactions are complex or multiple. © Birkhäuser Verlag, 2005.
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| 17. |
- Hirschberg, Daniel, et al.
(författare)
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N-terminal acetylation in a third protein family of vertebrate alcohol dehydrogenase/retinal reductase found through a 'proteomics' approach in enzyme characterization.
- 2001
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Ingår i: Cellular and Molecular Life Sciences (CMLS). - 1420-682X .- 1420-9071. ; 58:9
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Tidskriftsartikel (refereegranskat)abstract
- A recent finding of a novel class of retinol-active alcohol dehydrogenase (ADH) in frog prompted analysis of this activity in other vertebrate forms. Surprisingly, yet another and still more unrelated ADH was identified in chicken tissues. It was found to be a member of the aldo-keto reductase (AKR) enzyme family, not previously known as an ADH in vertebrates. Its terminal blocking group and the N-terminal segment, not assigned by protein and cDNA structure analysis, were determined by electrospray tandem mass spectrometry after protein isolation by two-dimensional gel electrophoresis. The N terminus is Acetyl-Ala- and the N-terminal segment contains two consecutive Asn residues. The results establish the new ADH enzyme of the AKR family and show the usefulness of combined gel separation and mass spectrometry in enzyme-characterization.
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| 18. |
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| 19. |
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| 20. |
- Jonsson, AP, et al.
(författare)
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A novel Ser O-glucuronidation in acidic proline-rich proteins identified by tandem mass spectrometry.
- 2000
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 475:2, s. 131-4
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Tidskriftsartikel (refereegranskat)abstract
- Human acidic proline-rich salivary protein PRP-1 and its C-terminally truncated form PRP-3 were analyzed by electrospray tandem mass spectrometry. Post-translational modifications were detected and characterized. A pyroglutamic acid residue was demonstrated at the N-terminus, Ser-8 and Ser-22 were shown to be phosphorylated and an O-linked glucuronic acid conjugation was identified. The latter modification was located to Ser-17 and found to be present in approximately 40% of the polypeptides.
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| 21. |
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| 22. |
- Jörnvall, H, et al.
(författare)
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The alcohol dehydrogenase system
- 1995
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Ingår i: Advances in experimental medicine and biology. - Boston, MA : Springer US. - 0065-2598. ; 372, s. 281-94
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Tidskriftsartikel (refereegranskat)
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| 23. |
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| 24. |
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| 25. |
- Landreh, M, et al.
(författare)
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The structure, molecular interactions and bioactivities of proinsulin C-peptide correlate with a tripartite molecule
- 2014
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Ingår i: Biomolecular concepts. - : Walter de Gruyter GmbH. - 1868-503X .- 1868-5021. ; 5:2, s. 109-18
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Tidskriftsartikel (refereegranskat)abstract
- Many biological roles have been assigned to proinsulin C-peptide over the years. Some appear surprisingly disparate and sometimes even contradictory, like chaperone-like actions and depository tendencies. This review summarizes recently reported biomolecular interactions of the peptide and presents how they correlate with structural and functional aspects into a partitioned molecular architecture. At the structural level, the C-peptide sequence and fold can be subdivided into three distinct parts (‘tripartite’). At the functional level, its chaperone-like abilities, self-assembly, and membrane interactions, as well as interactions with relevant proteins can be separately ascribed to these three segments. At the biological level, the assignments are compatible with the suggested roles of C-peptide in granular insulin storage, chaperone-like activities on insulin oligomers, possible depository tendencies, and proposed receptor interactions. Finally, the assignments give interesting parallels to further bioactive peptides, including glucagon and neurotensin. Provided pharmaceutical and clinical trials are successfully completed, the present interpretations should supply mechanistic explanations on C-peptide as a bioactive compound of importance in health and diabetes.
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| 26. |
- Landreh, M, et al.
(författare)
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Transthyretin microheterogeneity and molecular interactions: implications for amyloid formation
- 2014
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Ingår i: Biomolecular concepts. - : Walter de Gruyter GmbH. - 1868-503X .- 1868-5021. ; 5:3, s. 257-64
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Tidskriftsartikel (refereegranskat)abstract
- Aggregation of transthyretin (TTR), a plasma-binding protein for thyroxine and retinol-binding protein, is the cause of several amyloid diseases. Disease-associated mutations are well known, but wild-type TTR is, to a lesser extent, also amyloidogenic. Monomerization, not oligomer formation as in several other depository diseases, is the rate-limiting step in TTR aggregation, and stabilization of the natively tetrameric form can inhibit amyloid formation. Modifications on Cys10, as well as interactions with native ligands in plasma, were early found to influence the equilibrium between tetrameric and monomeric TTR by dissociating or stabilizing the tetramer. Following these discoveries, synthetic ligands for pharmacological prevention of TTR aggregation could be developed. In this article, we outline how the different types of TTR interactions and its microheterogeneity in plasma are related to its propensity to form amyloid fibrils. We conclude that plasma constituents and dietary components may act as natural TTR stabilizers whose mechanisms of action provide cues for the amelioration of TTR amyloid disease.
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| 27. |
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| 28. |
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| 29. |
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| 30. |
- Naseeb, U, et al.
(författare)
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Differential hemoglobin A sequestration between hemodialysis modalities
- 2017
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Ingår i: Biomolecular concepts. - : Walter de Gruyter GmbH. - 1868-503X .- 1868-5021. ; 8:2, s. 125-129
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Tidskriftsartikel (refereegranskat)abstract
- This report evaluates plasma protein patterns, dialysates and protein analysis of used dialysis membranes from the same patient under hemodialysis in three separate modalities, using high-flux membranes in concentration-driven transport (HD), convection-driven hemofiltration (HF) and combined hemodialfiltration (HDF). The plasma protein changes induced by each of the three dialysis modalities showed small differences in proteins identified towards our previous plasma analyses of chronic kidney disease (CKD) patients. The used dialysate peptide concentrations likewise exhibited small differences among the modalities and varied in the same relative order as the plasma changes, with protein losses in the order HD>HDF>HF. The membrane protein deposits allowed quantification of the relative Hb removal ratios as ~1.7 for HD and ~1.2 for HDF vs. ~1.0 for HF. Hence, plasma protein alterations, dialysate peptide contents and membrane Hb deposits all identify HD as the modality with the most extensive filtration results and exemplifies the accessibility of protein analysis of used membrane filters for evaluation of dialysis efficiencies.
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| 31. |
- Oppermann, U C T, et al.
(författare)
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Active site directed mutagenesis of 3 beta/17 beta-hydroxysteroid dehydrogenase establishes differential effects on short-chain dehydrogenase/reductase reactions
- 1997
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 36:1, s. 34-40
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Tidskriftsartikel (refereegranskat)abstract
- Mutagenetic replacements uf conserved residues within the active site of the short-chain dehydrogenase/reductase (SDR) superfamily were studied using prokaryotic 3 beta/17 beta-hydroxysteroid dehydrogenase (3 beta/17 beta-HSD) from Comamonas testosteroni as a model system. The results provide novel data to establish Ser138 as a member of a catalytically important ''triad'' of residues also involving Tyr151 and Lys155. A Ser --> Ala exchange at position 138 results in an almost complete (>99.9%) loss of enzymatic activity, which is not observed with a Ser --> Thr replacement. This indicates that an essential factor for catalysis is the ability of side chain 138 to form hydrogen bond interactions. Mutations in the NAD(H) binding region, in strands beta A, beta D, and adjacent turns, reveal two additional residues, Thr12 and Asn87, which are important for correct binding of the coenzyme aad with a differential effect on the reactions catalyzed. Thus, mutation of Thr12 to Ala results in a complete loss of the 3 beta-dehydrogenase activity, whereas the 3-oxoreductase activity remains unchanged. On the other hand, a T12S substitution yields a protein with unaltered catalytic constants for both reactions, revealing that a specific hydrogen bond is critical for the dehydrogenase activity. Our interpretation of the available crystal structure of 3 alpha/20 beta-HSD from Streptomyces hydrogenans suggests a hydrogen her-id in that enzyme between the Thr12 side chain and the backbone NW of Asn87 rather than the coenzyme, indicating that this hydrogen bond to the beta D strand might determine a crucial difference between the reductive and the oxidative reaction types. Similarly, mutation of Asn87 to Ala results in an 80% reduction of K-cat/K-m in the dehydrogenase direction but also unchanged 3-oxoreductase propel ties. It appears that the binding of NAD(+) to the protein is influenced by local structural changes involving strand beta D and beta A to alpha B.
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| 32. |
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| 33. |
- Persson, B, et al.
(författare)
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Short-chain dehydrogenases/reductases
- 1995
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Ingår i: Advances in experimental medicine and biology. - Boston, MA : Springer US. - 0065-2598. ; 372, s. 383-95
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Tidskriftsartikel (refereegranskat)
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| 34. |
- Sima, AA, et al.
(författare)
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Proinsulin C-peptide--a consensus statement
- 2001
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Ingår i: International journal of experimental diabetes research. - : Hindawi Limited. - 1560-4284. ; 2:2, s. 145-51
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Tidskriftsartikel (refereegranskat)abstract
- In recent years the physiological role of the proinsulin C-peptide has received increasing attention, focusing on the potential therapeutic value of C-peptide replacement in preventing and ameliorating type 1 diabetic complications. In order to consolidate these new data and to identify the immediate directions of C-peptide research and its clinical usefulness, an International Symposium was held in Detroit, Michigan, on October 20–21, 2000, under the auspices of the Wayne State University/Morris Hood Jr. Comprehensive Diabetes Center. In this communication, we review the cellular, physiological and clinical effects of C-peptide replacement in animal models and in patients with type 1 diabetes. Finally, recommendations are presented as to the most urgent studies that should be pursued to further establish the biological action of C-peptide and its therapeutic value.
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| 35. |
- Spyrou, Giannis, et al.
(författare)
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Characterization of the flavin reductase gene (fre) of Escherichia coli and construction of a plasmid for overproduction of the enzyme
- 1991
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Ingår i: Journal of Bacteriology. - : American Society for Microbiology. - 0021-9193 .- 1098-5530. ; 173:12, s. 3673-3679
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Tidskriftsartikel (refereegranskat)abstract
- The enzyme NAD(P)H:flavin oxidoreductase (flavin reductase) catalyzes the reduction of soluble flavins by reduced pyridine nucleotides. In Escherichia coli it is part of a multienzyme system that reduces the Fe(III) center of ribonucleotide reductase to Fe(II) and thereby sets the stage for the generation by dioxygen of a free tyrosyl radical required for enzyme activity. Similar enzymes are known in other organisms and may more generally be involved in iron metabolism. We have now isolated the gene for the E. coli flavin reductase from a lambda gt11 library. After DNA sequencing we found an open reading frame coding for a polypeptide of 233 amino acids, with a molecular weight of 26,212 and with an N-terminal segment identical to that determined by direct Edman degradation. The coding sequence is preceded by a weak ribosome binding site centered 8 nucleotides from the start codon and by a promoterlike sequence centered at a distance of 83 nucleotides. In a Kohara library the gene hybridized to position 3680 on the physical map of E. coli. A bacterial strain that overproduced the enzyme approximately 100-fold was constructed. The translated amino acid sequence contained a potential pyridine nucleotide-binding site and showed 25% identity with the C-terminal part of one subunit (protein C) of methane monooxygenase from methanotropic bacteria that reduces the iron center of a second subunit (protein A) of the oxygenase by pyridine nucleotides.
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| 36. |
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| 37. |
- Wallén, P, et al.
(författare)
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Purification and characterization of a melanoma cell plasminogen activator.
- 1983
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Ingår i: European Journal of Biochemistry. - 0014-2956 .- 1432-1033. ; 132:3, s. 681-6
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Tidskriftsartikel (refereegranskat)abstract
- The plasminogen activator from a human melanoma cell line was purified with immunoadsorption as a major step. The cells were cultured in the presence of aprotinin in order to avoid proteolysis. A three-step purification involved adsorption on antibodies to porcine tissue plasminogen activator before chromatographies on arginine-Sepharose and Sephadex G-150. All solvents contained Tween-80 (0.01%) and, except for the last step, aprotinin. The final product had a specific activity of about 220000 IU/mg measured against the WHO urokinase standard. The activator obtained has an apparent Mr of 72000 and consists of single-chain molecules. Evidence was obtained that four different types of activator variants occur. First and known previously, the one-chain form can be proteolytically cleaved into a two-chain form. Secondly, both the one-chain and two-chain molecules exhibit two forms with molecular weight differences of about 3000 (possibly due to carbohydrate differences). Thirdly, the one-chain preparations contain two variants, each constituting about 50% of the material and differing in length by three N-terminal amino acids. Finally, a possible positional microheterogeneity was detected. Digestion with plasmin yields the two-chain form with disulfide-bonded polypeptide chains, 'A' and 'B' (from the N-terminal and C-terminal parts, respectively). At the same time, the variability of the original N terminus is removed. The A chain keeps the two Mr variants (now about 40000 and 37000, respectively). The B chain (Mr about 33000) contains the active site of the molecule, as demonstrated by labelling with [3H]diisopropyl phosphofluoridate, and is homologous to the enzymatically active chains of thrombin, plasmin and other serine proteases. In contrast to these enzymes, the plasminogen activator is enzymatically active in the one-chain form. A speculative explanation for this activity may possibly be the presence of an epsilon-amino group of a lysine residue at a position close to the bond cleaved in the two-chain form.
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| 38. |
- Wu, X., et al.
(författare)
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Codon optimization reveals critical factors for high level expression of two rare codon genes in Escherichia coli : RNA stability and secondary structure but not tRNA abundance
- 2004
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 313:1, s. 89-96
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Tidskriftsartikel (refereegranskat)abstract
- Expression patterns in Escherichia coli of two small archaeal proteins with a natural content of about 30% rare codons were analyzed. The proteins, a histone-like protein from Sulfolobus shibatae (Ssh10), and a glutaredoxin-like protein from Methanobacterium thermoautotrophicum (mtGrx), were produced with expression plasmids encoding wild-type genes, codon-optimized synthetic, and GST-fusion genes. These constructs were expressed in BL21 (DE3), its LysS derivative, and modified strains carrying copies for rare codon tRNAs or deletions in the RNAseE gene. Both Ssh10 and mtGrx expression levels were constitutively high in BL21(DE3) and its derivatives, with the exception of the LysS phenotype, which prevented high level expression of the Ssh10 wild-type gene. Surprisingly, a codon-optimized mtGrx gene construct displayed undetectable levels of protein production. The translational block observed with the synthetic mtGrx gene could be circumvented by using a synthetic mtGrx-glutathione S-transferase (GST) fusion construct or by in vitro translation. Taken together, the results underscore the importance of mRNA levels and RNA stability, but not necessarily tRNA abundance for efficient heterologous protein production in E. coli.
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| 39. |
- Wu, X, et al.
(författare)
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Thermal unfolding of the archaeal DNA and RNA binding protein Ssh10
- 2008
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 373:4, s. 482-487
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Tidskriftsartikel (refereegranskat)abstract
- The reversible thermal unfolding of the archaeal histone-like protein Ssh10b from the extremophile Sulfolobus shibatae was studied using differential scanning calorimetry and circular dichroism spectroscopy. Analytical ultracentrifugation and gel filtration showed that Ssh10b is a stable dimer in the pH range 2.5-7.0. Thermal denaturation data fit into a two-state unfolding model, suggesting that the Ssh10 dimer unfolds as a single cooperative unit with a maximal melting temperature of 99.9 degrees C and an enthalpy change of 134 kcal/mol at pH 7.0. The heat capacity change upon unfolding determined from linear fits of the temperature dependence of DeltaH(cal) is 2.55 kcal/(mol K). The low specific heat capacity change of 13 cal/(mol K residue) leads to a considerable flattening of the protein stability curve (DeltaG (T)) and results in a maximal DeltaG of only 9.5 kcal/mol at 320 K and a DeltaG of only 6.0 kcal/mol at the optimal growth temperature of Sulfolobus.
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