| 1. |
- Schubert, Maria, et al.
(författare)
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Proteome Map of the Chloroplast Lumen of Arabidopsis thaliana
- 2002
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 277:10, s. 8354-8365
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Tidskriftsartikel (refereegranskat)abstract
- The thylakoid membrane of the chloroplast is the center of oxygenic photosynthesis. To better understand the function of the luminal compartment within the thylakoid network, we have carried out a systematic characterization of the luminal thylakoid proteins from the model organism Arabidopsis thaliana. Our data show that the thylakoid lumen has its own specific proteome, of which 36 proteins were identified. Besides a large group of peptidyl-prolyl cis-trans isomerases and proteases, a family of novel PsbP domain proteins was found. An analysis of the luminal signal peptides showed that 19 of 36 luminal precursors were marked by a twin-arginine motif for import via the Tat pathway. To compare the model organism Arabidopsis with another typical higher plant, we investigated the proteome from the thylakoid lumen of spinach and found that the luminal proteins from both plants corresponded well. As a complement to our experimental investigation, we made a theoretical prediction of the luminal proteins from the whole Arabidopsis genome and estimated that the thylakoid lumen of the chloroplast contains ~80 proteins.
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| 2. |
- Abelein, Axel, et al.
(författare)
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Formation of dynamic soluble surfactant-induced amyloid β peptide aggregation intermediates
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:32, s. 23518-23528
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Tidskriftsartikel (refereegranskat)abstract
- Intermediate amyloidogenic states along the amyloid β peptide (Aβ) aggregation pathway have been shown to be linked to neurotoxicity. To shed more light on the different structures that may arise during Aβ aggregation, we here investigate surfactant-induced Aβ aggregation. This process leads to co-aggregates featuring a β-structure motif that is characteristic for mature amyloid-like structures. Surfactants induce secondary structure in Aβ in a concentration-dependent manner, from predominantly random coil at low surfactant concentration, via β-structure to the fully formed α-helical state at high surfactant concentration. The β-rich state is the most aggregation-prone as monitored by thioflavin T fluorescence. Small angle x-ray scattering reveals initial globular structures of surfactant-Aβ co-aggregated oligomers and formation of elongated fibrils during a slow aggregation process. Alongside this slow (minutes to hours time scale) fibrillation process, much faster dynamic exchange (k(ex) ∼1100 s(-1)) takes place between free and co-aggregate-bound peptide. The two hydrophobic segments of the peptide are directly involved in the chemical exchange and interact with the hydrophobic part of the co-aggregates. Our findings suggest a model for surfactant-induced aggregation where free peptide and surfactant initially co-aggregate to dynamic globular oligomers and eventually form elongated fibrils. When interacting with β-structure promoting substances, such as surfactants, Aβ is kinetically driven toward an aggregation-prone state.
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| 3. |
- Adlerz, Linda, et al.
(författare)
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IGF-1-induced Processing of the Amyloid Precursor Protein Family Is Mediated by Different Signaling Pathways
- 2007
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 282:14, s. 10203-10209
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Tidskriftsartikel (refereegranskat)abstract
- The mammalian amyloid precursor protein (APP) protein family consists of the APP and the amyloid precursor-like proteins 1 and 2 (APLP1 and APLP2). The neurotoxic amyloid beta-peptide (Abeta) originates from APP, which is the only member of this protein family implicated in Alzheimer disease. However, the three homologous proteins have been proposed to be processed in similar ways and to have essential and overlapping functions. Therefore, it is also important to take into account the effects on the processing and function of the APP-like proteins in the development of therapeutic drugs aimed at decreasing the production of Abeta. Insulin and insulin-like growth factor-1 (IGF-1) have been shown to regulate APP processing and the levels of Abeta in the brain. In the present study, we show that IGF-1 increases alpha-secretase processing of endogenous APP and also increases ectodomain shedding of APLP1 and APLP2 in human SH-SY5Y neuroblastoma cells. We also investigated the role of different IGF-1-induced signaling pathways, using specific inhibitors for phosphatidylinositol 3-kinase and mitogen-activated protein kinase (MAPK). Our results indicate that phosphatidylinositol 3-kinase is involved in ectodomain shedding of APP and APLP1, but not APLP2, and that MAPK is involved only in the ectodomain shedding of APLP1.
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| 4. |
- Andréasson, Claes, et al.
(författare)
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The endoplasmic reticulum Grp170 acts as a nucleotide exchange factor of Hsp70 via a mechanism similar to that of the cytosolic Hsp11
- 2010
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 285:16, s. 12445-53
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Tidskriftsartikel (refereegranskat)abstract
- Grp170 and Hsp110 proteins constitute two evolutionary distinct branches of the Hsp70 family that share the ability to function as nucleotide exchange factors (NEFs) for canonical Hsp70s. Although the NEF mechanism of the cytoplasmic Hsp110s is well understood, little is known regarding the mechanism used by Grp170s in the endoplasmic reticulum. In this study, we compare the yeast Grp170 Lhs1 with the yeast Hsp110 Sse1. We find that residues important for Sse1 NEF activity are conserved in Lhs1 and that mutations in these residues in Lhs1 compromise NEF activity. As previously reported for Sse1, Lhs1 requires ATP to trigger nucleotide exchange in its cognate Hsp70 partner Kar2. Using site-specific cross-linking, we show that the nucleotide-binding domain (NBD) of Lhs1 interacts with the NBD of Kar2 face to face, and that Lhs1 contacts the side of the Kar2 NBD via its protruding C-terminal alpha-helical domain. To directly address the mechanism of nucleotide exchange, we have compared the hydrogen-exchange characteristics of a yeast Hsp70 NBD (Ssa1) in complex with either Sse1 or Lhs1. We find that Lhs1 and Sse1 induce very similar changes in the conformational dynamics in the Hsp70. Thus, our findings demonstrate that despite some differences between Hsp110 and Grp170 proteins, they use a similar mechanism to trigger nucleotide exchange.
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| 5. |
- Assarsson, Maria, et al.
(författare)
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Restoring proper radical generation by azide binding to the iron site of the E238A mutant R2 protein of ribonucleotide reductase from Escherichia coli.
- 2001
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 276:29, s. 26852-26859
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Tidskriftsartikel (refereegranskat)abstract
- The enzyme activity of Escherichia coli ribonucleotide reductase requires the presence of a stable tyrosyl free radical and diiron center in its smaller R2 component. The iron/radical site is formed in a reconstitution reaction between ferrous iron and molecular oxygen in the protein. The reaction is known to proceed via a paramagnetic intermediate X, formally a Fe(III)-Fe(IV) state. We have used 9.6 GHz and 285 GHz EPR to investigate intermediates in the reconstitution reaction in the iron ligand mutant R2 E238A with or without azide, formate, or acetate present. Paramagnetic intermediates, i.e. a long-living X-like intermediate and a transient tyrosyl radical, were observed only with azide and under none of the other conditions. A crystal structure of the mutant protein R2 E238A/Y122F with a diferrous iron site complexed with azide was determined. Azide was found to be a bridging ligand and the absent Glu-238 ligand was compensated for by azide and an extra coordination from Glu-204. A general scheme for the reconstitution reaction is presented based on EPR and structure results. This indicates that tyrosyl radical generation requires a specific ligand coordination with 4-coordinate Fe1 and 6-coordinate Fe2 after oxygen binding to the diferrous site.
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| 6. |
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| 7. |
- Bakali, Amin, et al.
(författare)
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Crystal structure of YegS, a homologue to the mammalian diacylglycerol kinases, reveals a novel regulatory metal binding site
- 2007
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 282:27, s. 19644-19652
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Tidskriftsartikel (refereegranskat)abstract
- The human lipid kinase family controls cell proliferation, differentiation, and tumorigenesis and includes diacylglycerol kinases, sphingosine kinases, and ceramide kinases. YegS is an Escherichia coli protein with significant sequence homology to the catalytic domain of the human lipid kinases. We have solved the crystal structure of YegS and shown that it is a lipid kinase with phosphatidylglycerol kinase activity. The crystal structure reveals a two-domain protein with significant structural similarity to a family of NAD kinases. The active site is located in the interdomain cleft formed by four conserved sequence motifs. Surprisingly, the structure reveals a novel metal binding site composed of residues conserved in most lipid kinases.
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| 8. |
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| 9. |
- Berg, Stefan, et al.
(författare)
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Sequence properties of the 1,2-diacylglycerol 3-glucosyltransferase from Acholeplasma laidlawii membranes : Recognition of a large group of lipid glycosyltransferases in eubacteria and archaea
- 2001
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 276:25, s. 22056-22063
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of the nonbilayer-prone α-monoglucosyldiacylglycerol (MGlcDAG) is crucial for bilayer packing properties and the lipid surface charge density in the membrane ofAcholeplasma laidlawii. The gene for the responsible, membrane-bound glucosyltransferase (alMGS) (EC 2.4.1.157) was sequenced and functionally cloned in Escherichia coli, yielding MGlcDAG in the recombinants. Similar amino acid sequences were encoded in the genomes of several Gram-positive bacteria (especially pathogens), thermophiles, archaea, and a few eukaryotes. All of these contained the typical EX7E catalytic motif of the CAZy family 4 of α-glycosyltransferases. The synthesis of MGlcDAG by a close sequence analog from Streptococcus pneumoniae (spMGS) was verified by polymerase chain reaction cloning, corroborating a connection between sequence and functional similarity for these proteins. However, alMGS and spMGS varied in dependence on anionic phospholipid activators phosphatidylglycerol and cardiolipin, suggesting certain regulatory differences. Fold predictions strongly indicated a similarity for alMGS (and spMGS) with the two-domain structure of the E. coli MurG cell envelope glycosyltransferase and several amphipathic membrane-binding segments in various proteins. On the basis of this structure, the alMGS sequence charge distribution, and anionic phospholipid dependence, a model for the bilayer surface binding and activity is proposed for this regulatory enzyme.
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| 10. |
- Berggren, Gustav, et al.
(författare)
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Semiquinone-induced Maturation of Bacillus anthracis Ribonucleotide Reductase by a Superoxide Intermediate
- 2014
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 289:46, s. 31940-31949
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Tidskriftsartikel (refereegranskat)abstract
- Background: Activation of ribonucleotide reductase Ib depends on the flavodoxin-like maturase NrdI.Results: The redox properties of Bacillus anthracis NrdI allow isolation of the semiquinone state, NrdI(sq), which can catalyze formation of the manganese-tyrosyl radical cofactor.Conclusion: The maturation capacity of NrdI(sq) provides evidence that Mn-NrdF is activated via a superoxide radical.Significance: Novel antibiotics may be designed to selectively target the maturation mechanism.
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