| 1. |
- Claesson, Magnus, et al.
(författare)
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Crystal structure of the glycosyltransferase SnogD from the biosynthetic pathway of nogalamycin in Streptomyces nogalater
- 2012
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Ingår i: The FEBS journal. - Stockholm : Karolinska Institutet, Dept of Medical Biochemistry and Biophysics. - 1742-464X .- 1742-4658.
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Tidskriftsartikel (refereegranskat)abstract
- The glycosyltransferase SnogD from Streptomyces nogalater transfers a nogalamine moiety to the metabolic intermediate 3′,4′-demethoxynogalose-1-hydroxynogalamycinone during the final steps of biosynthesis of the aromatic polyketide nogalamycin. The crystal structure of recombinant SnogD, as an apo-enzyme and with a bound nucleotide, 2-deoxyuridine-5′-diphosphate, was determined to 2.6 Å resolution. Reductive methylation of SnogD was crucial for reproducible preparation of diffraction quality crystals due to creation of an additional intermolecular salt bridge between methylated lysine residue Lys384 and Glu374* from an adjacent molecule in the crystal lattice. SnogD is a dimer both in solution and in the crystal, and the enzyme subunit displays a fold characteristic of the GT-B family of glycosyltransferases. Binding of the nucleotide is associated with rearrangement of two active-site loops. Site-directed mutagenesis shows that two active-site histidine residues, His25 and His301, are critical for the glycosyltransferase activities of SnogD both in vivo and in vitro. The crystal structures and the functional data are consistent with a role for His301 in binding of the diphosphate group of the sugar donor substrate, and a function of His25 as a catalytic base in the glycosyl transfer reaction.
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| 2. |
- Andersen, Gorm, et al.
(författare)
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A gene duplication led to specialized gamma-aminobutyrate and beta-alanine aminotransferase in yeast
- 2007
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 274:7, s. 1804-1817
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Tidskriftsartikel (refereegranskat)abstract
- In humans, beta-alanine (BAL) and the neurotransmitter gamma-aminobutyrate (GABA) are transaminated by a single aminotransferase enzyme. Apparently, yeast originally also had a single enzyme, but the corresponding gene was duplicated in the Saccharomyces kluyveri lineage. SkUGA1 encodes a homologue of Saccharomyces cerevisiae GABA aminotransferase, and SkPYD4 encodes an enzyme involved in both BAL and GABA transamination. SkPYD4 and SkUGA1 as well as S. cerevisiae UGA1 and Schizosaccharomyces pombe UGA1 were subcloned, over-expressed and purified. One discontinuous and two continuous coupled assays were used to characterize the substrate specificity and kinetic parameters of the four enzymes. It was found that the cofactor pyridoxal 5'-phosphate is needed for enzymatic activity and alpha-ketoglutarate, and not pyruvate, as the amino group acceptor. SkPyd4p preferentially uses BAL as the amino group donor (V-max/K-m = 0.78 U.mg(-1).mM(-1)), but can also use GABA (V-max/K-m = 0.42 U.mg(-1).mM(-1)), while SkUga1p only uses GABA (V-max/K-m = 4.01 U.mg(-1).mM(-1)). SpUga1p and ScUga1p transaminate only GABA and not BAL. While mammals degrade BAL and GABA with only one enzyme, but in different tissues, S. kluyveri and related yeasts have two different genes/enzymes to apparently 'distinguish' between the two reactions in a single cell. It is likely that upon duplication similar to 200 million years ago, a specialized Uga1p evolved into a 'novel' transaminase enzyme with broader substrate specificity.
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| 3. |
- Czerwiec, E, et al.
(författare)
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Novel gamma-carboxyglutamic acid-containing peptides from the venom of Conus textile
- 2006
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 273:12, s. 2779-2788
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Tidskriftsartikel (refereegranskat)abstract
- The cone snail is the only invertebrate system in which the vitamin K-dependent carboxylase (or gamma-carboxylase) and its product gamma-carboxyglutamic acid (Gla) have been identified. It remains the sole source of structural information of invertebrate gamma-carboxylase substrates. Four novel Gla-containing peptides were purified from the venom of Conus textile and characterized using biochemical methods and mass spectrometry. The peptides Gla(1)-TxVI, Gla(2)-TxVI/A, Gla(2)-TxVI/B and Gla(3)-TxVI each have six Cys residues and belong to the O-superfamily of conotoxins. All four conopeptides contain 4-trans-hydroxyproline and the unusual amino acid 6-L >-bromotryptophan. Gla(2)-TxVI/A and Gla(2)-TxVI/B are isoforms with an amidated C-terminus that differ at positions +1 and +13. Three isoforms of Gla(3)-TxVI were observed that differ at position +7: Gla(3)-TxVI, Glu7-Gla(3)-TxVI and Asp7-Gla(3)-TxVI. The cDNAs encoding the precursors of the four peptides were cloned. The predicted signal sequences (amino acids -46 to -27) were nearly identical and highly hydrophobic. The predicted propeptide region (-20 to -1) that contains the gamma-carboxylation recognition site (gamma-CRS) is very similar in Gla(2)-TxVI/A, Gla(2)-TxVI/B and Gla(3)-TxVI, but is more divergent for Gla(1)-TxVI. Kinetic studies utilizing the Conus gamma-carboxylase and synthetic peptide substrates localized the gamma-CRS of Gla(1)-TxVI to the region -14 to -1 of the polypeptide precursor: the K-m was reduced from 1.8 mM for Gla (1)-TxVI lacking a propeptide to 24 mu M when a 14-residue propeptide was attached to the substrate. Similarly, addition of an 18-residue propeptide to Gla(2)-TxVI/B reduced the K-m value tenfold.
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| 4. |
- Hellstrand, Erik, et al.
(författare)
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Complete high-density lipoproteins in nanoparticle corona.
- 2009
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 276:12, s. 3372-3381
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Tidskriftsartikel (refereegranskat)abstract
- In a biological environment, nanoparticles immediately become covered by an evolving corona of biomolecules, which gives a biological identity to the nanoparticle and determines its biological impact and fate. Previous efforts at describing the corona have concerned only its protein content. Here, for the first time, we show, using size exclusion chromatography, NMR, and pull-down experiments, that copolymer nanoparticles bind cholesterol, triglycerides and phospholipids from human plasma, and that the binding reaches saturation. The lipid and protein binding patterns correspond closely with the composition of high-density lipoprotein (HDL). By using fractionated lipoproteins, we show that HDL binds to copolymer nanoparticles with much higher specificity than other lipoproteins, probably mediated by apolipoprotein A-I. Together with the previously identified protein binding patterns in the corona, our results imply that copolymer nanoparticles bind complete HDL complexes, and may be recognized by living systems as HDL complexes, opening up these transport pathways to nanoparticles. Apolipoproteins have been identified as binding to many other nanoparticles, suggesting that lipid and lipoprotein binding is a general feature of nanoparticles under physiological conditions.
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| 5. |
- Langerholc, T, et al.
(författare)
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Inhibitory properties of cystatin F and its localization in U937 promonocyte cells
- 2005
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 272:6, s. 1535-1545
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Tidskriftsartikel (refereegranskat)abstract
- Cystatin F is a recently discovered type II cystatin expressed almost exclusively in immune cells. It is present intracellularly in lysosome-like vesicles, which suggests a potential role in regulating papain-like cathepsins involved in antigen presentation. Therefore, interactions of cystatin F with several of its potential targets, cathepsins F, K, V, S, H, X and C, were studied in vitro. Cystatin F tightly inhibited cathepsins F, K and V with K-i values ranging from 0.17 nm to 0.35 nm, whereas cathepsins S and H were inhibited with 100-fold lower affinities (K-i approximate to 30 nm). The exopeptidases, cathepsins C and X were not inhibited by cystatin F. In order to investigate the biological significance of the inhibition data, the intracellular localization of cystatin F and its potential targets, cathepsins B, H, L, S, C and K, were studied by confocal microscopy in U937 promonocyte cells. Although vesicular staining was observed for all the enzymes, only cathepsins H and X were found to be colocalized with the inhibitor. This suggests that cystatin F in U937 cells may function as a regulatory inhibitor of proteolytic activity of cathepsin H or, more likely, as a protection against cathepsins misdirected to specific cystatin F containing endosomal/lysosomal vesicles. The finding that cystatin F was not colocalized with cystatin C suggests distinct functions for these two cysteine protease inhibitors in U937 cells.
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| 6. |
- Masuyer, Geoffrey, et al.
(författare)
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Inhibition mechanism of human galectin-7 by a novel galactose- benzylphosphate inhibitor
- 2012
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 279:2, s. 193-202
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Tidskriftsartikel (refereegranskat)abstract
- Galectins are involved in many cellular processes due to their ability to bind carbohydrates. Understanding their functions has shown the necessity for potent and specific galectin inhibitors. Human galectin-7 (hGal-7), in particular, has been highlighted as an important marker in many types of cancer by either inhibiting or promoting tumour growth. Producing ligands able to selectively target hGal-7 will offer promising tools for deciphering cancer processes in which hGal-7 is involved as well as present potential solutions for future therapeutics. Here we report the high resolution crystal structure of hGal-7 in complex with a synthetic 2-O-benzylphosphate-galactoside inhibitor (which is > 60-fold more potent than its parent galactoside). The high resolution crystallographic analysis highlights the validity of using saccharide derivatives, conserving properties of the galactose binding, while enhanced affinity and specificity is provided by the added phosphate group. This structural information will allow the design of further inhibitors with improved potency and specificity.
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| 7. |
- Rydengård, Victoria, et al.
(författare)
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Histidine-rich glycoprotein exerts antibacterial activity
- 2007
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 274:2, s. 377-389
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Tidskriftsartikel (refereegranskat)abstract
- Histidine-rich glycoprotein (HRGP), an abundant heparin-binding protein found in plasma and thrombocytes, exerts antibacterial effects against Gram-positive bacteria (Enterococcus faecalis and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Fluorescence studies and electron microscopy to assess membrane permeation showed that HRGP induces lysis of E. faecalisbacteria in the presence of Zn2+ or at low pH. Heparin blocked binding of the protein to E. faecalis and abolished antibacterial activity. Furthermore, truncated HRGP, devoid of the heparin-binding and histidine-rich domain, was not antibacterial. It has previously been shown that peptides containing consensus heparin-binding sequences (Cardin and Weintraub motifs) are antibacterial. Thus, the peptide (GHHPH)4, derived from the histidine-rich region of HRGP and containing such a heparin-binding motif, was antibacterial for E. faecalis in the presence of Zn2+ or at low pH. The results show a previously undisclosed antibacterial activity of HRGP and suggest that the histidine-rich and heparin-binding domain of HRGP mediates the antibacterial activity of the protein.
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| 8. |
- Johansson, Renzo, et al.
(författare)
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High-resolution crystal structures of the flavoprotein NrdI in oxidized and reduced states – an unusual flavodoxin
- 2010
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 277:20, s. 4265-4277
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Tidskriftsartikel (refereegranskat)abstract
- The small flavoprotein NrdI is an essential component of the class Ib ribonucleotide reductase system in many bacteria. NrdI interacts with the class Ib radical generating protein NrdF. It is suggested to be involved in the rescue of inactivated diferric centres or generation of active dimanganese centres in NrdF. Although NrdI bears a superficial resemblance to flavodoxin, its redox properties have been demonstrated to be strikingly different. In particular, NrdI is capable of two-electron reduction, whereas flavodoxins are exclusively one-electron reductants. This has been suggested to depend on a lesser destabilization of the negatively-charged hydroquinone state than in flavodoxins. We have determined the crystal structures of NrdI from Bacillus anthracis, the causative agent of anthrax, in the oxidized and semiquinone forms, at resolutions of 0.96 and 1.4 Å, respectively. These structures, coupled with analysis of all curated NrdI sequences, suggest that NrdI defines a new structural family within the flavodoxin superfamily. The conformational behaviour of NrdI in response to FMN reduction is very similar to that of flavodoxins, involving a peptide flip in a loop near the N5 atom of the flavin ring. However, NrdI is much less negatively charged than flavodoxins, which is expected to affect its redox properties significantly. Indeed, sequence analysis shows a remarkable spread in the predicted isoelectric points of NrdIs, from approximately pH 4–10. The implications of these observations for class Ib ribonucleotide reductase function are discussed.
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| 9. |
- Mossberg, Anki, et al.
(författare)
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Structure and function of human α-lactalbumin made lethal to tumor cells (HAMLET)-type complexes.
- 2010
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 277:22, s. 4614-4625
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Forskningsöversikt (refereegranskat)abstract
- Human α-lactalbumin made lethal to tumor cells (HAMLET) and equine lysozyme with oleic acid (ELOA) are complexes consisting of protein and fatty acid that exhibit cytotoxic activities, drastically differing from the activity of their respective proteinaceous compounds. Since the discovery of HAMLET in the 1990s, a wealth of information has been accumulated, illuminating the structural, functional and therapeutic properties of protein complexes with oleic acid, which is summarized in this review. In vitro, both HAMLET and ELOA are produced by using ion-exchange columns preconditioned with oleic acid. However, the complex of human α-lactalbumin with oleic acid with the antitumor activity of HAMLET was found to be naturally present in the acidic fraction of human milk, where it was discovered by serendipity. Structural studies have shown that α-lactalbumin in HAMLET and lysozyme in ELOA are partially unfolded, 'molten-globule'-like, thereby rendering the complexes dynamic and in conformational exchange. HAMLET exists in the monomeric form, whereas ELOA mostly exists as oligomers and the fatty acid stoichiometry varies, with HAMLET holding an average of approximately five oleic acid molecules, whereas ELOA contains a considerably larger number (11- 48). Potent tumoricidal activity is found in both HAMLET and ELOA, and HAMLET has also shown strong potential as an antitumor drug in different in vivo animal models and clinical studies. The gain of new, beneficial function upon partial protein unfolding and fatty acid binding is a remarkable phenomenon, and may reflect a significant generic route of functional diversification of proteins via varying their conformational states and associated ligands.
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| 10. |
- Zameitat, Elke, et al.
(författare)
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Biochemical characterization of recombinant dihydroorotate dehydrogenase from the opportunistic yeast Candida albicans
- 2006
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 273:14, s. 3183-3191
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Tidskriftsartikel (refereegranskat)abstract
- Candida albicans is the most prevalent yeast pathogen in humans, and recently it has become increasingly resistant to the current antifungal agents. In this study we investigated C. albicans dihydroorotate dehydrogenase (DHODH, EC 1.3.99.11), which catalyzes the fourth step of de novo pyrimidine synthesis, as a new target for controlling infection. We propose that the enzyme is a member of the DHODH family 2, which comprises mitochondrially bound enzymes, with quinone as the direct electron acceptor and oxygen as the final electron acceptor. Full-length DHODH and N-terminally truncated DHODH, which lacks the targeting sequence and the transmembrane domain, were subcloned from C. albicans, recombinantly expressed in Escherichia coli, purified, and characterized for their kinetics and substrate specificity. An inhibitor screening with 28 selected compounds was performed. Only the dianisidine derivative, redoxal, and the biphenyl quinoline-carboxylic acid derivative, brequinar sodium, which are known to be potent inhibitors of mammalian DHODH, markedly reduced C. albicans DHODH activity. This study provides a background for the development of antipyrimidines with high efficacy for decreasing in situ pyrimidine nucleotide pools in C. albicans.
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