Eva Zerovnik
Research interests
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InterestsNeurodegeneration, Protein Aggregation, Amyloid, Protein Folding
Publications
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11.05Impact points
Impaired autophagy: a link between neurodegenerative diseases and progressive myoclonus epilepsies.
Trends in molecular medicine. 06/2011; 17(6):293-300.
In recent years, research into the molecular bases of neurodegenerative diseases has progressed, and therapies have been developed to combat the causative agents. Based on the observation that progressive myoclonus epilepsies (PMEs) and neurodegenerative diseases share common features of neurodegene... [more] In recent years, research into the molecular bases of neurodegenerative diseases has progressed, and therapies have been developed to combat the causative agents. Based on the observation that progressive myoclonus epilepsies (PMEs) and neurodegenerative diseases share common features of neurodegeneration, we propose that the two pathologies share common underlying molecular characteristics. It is well documented that autophagy is overloaded or impaired in neurodegenerative conditions, and it is also impaired in some PMEs, the clearest example being EPM2 (Lafora disease). Although more research into this connection is warranted, we propose that existing therapies for PMEs could be augmented with similar drugs as those used for neurodegenerative diseases.
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4.39Impact points
Modulation of contact order effects in the two-state folding of stefins A and B.
Biophysical journal. 05/2011; 100(9):2268-74.
It is well established that contact order and folding rates are correlated for small proteins. The folding rates of stefins A and B differ by nearly two orders of magnitude despite sharing an identical native fold and hence contact order. We break down the determinants of this behavior and demonstra... [more] It is well established that contact order and folding rates are correlated for small proteins. The folding rates of stefins A and B differ by nearly two orders of magnitude despite sharing an identical native fold and hence contact order. We break down the determinants of this behavior and demonstrate that the modulation of contact order effects can be accounted for by the combined contributions of a framework-like mechanism, characterized by intrinsic helix stabilities, together with nonnative helical backbone conformation and nonnative hydrophobic interactions within the folding transition state. These contributions result in the formation of nonnative interactions in the transition state as evidenced by the opposing effects on folding rate and stability of these proteins.
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5.13Impact points
Binding of amyloid peptides to domain-swapped dimers of other amyloid-forming proteins may prevent their neurotoxicity.
BioEssays : news and reviews in molecular, cellular and developmental biology. 12/2010; 32(12):1020-4.
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3.90Impact points
Amyloid fibril formation by human stefins: Structure, mechanism & putative functions.
Biochimie. 11/2010; 92(11):1597-607.
Many questions in the field of protein aggregation to amyloid fibrils remain open. In this review we describe predominantly in vitro studies of oligomerization and amyloid fibril formation by human stefins A and B. In human stefin B amyloidogenesis in vitro we have observed some general and many spe... [more] Many questions in the field of protein aggregation to amyloid fibrils remain open. In this review we describe predominantly in vitro studies of oligomerization and amyloid fibril formation by human stefins A and B. In human stefin B amyloidogenesis in vitro we have observed some general and many specific properties of its prefibrillar oligomers and amyloid fibrils. One characteristic feature in common to stefins and cystatins (and possibly some other amyloid proteins) is domain-swapping. In addition to solution structure of the domain-swapped dimer of stefin A, we recently have determined 3D structure of stefin B tetramer, which proved to be composed from two domain-swapped dimers, whose interaction occurs by a proline switch in the loop surrounding the conserved Pro 74. Studying the mechanism of fibril formation by stefin B, we found that the nucleation and fibril elongation reactions have energies of activation (E(a)'s) in the range of proline isomerisation, strongly indicating importance of the Pro at site 74 and/or other prolines in the sequence. Correlation between toxicity of the prefibrillar oligomers and their interaction with acidic phospholipids was demonstrated. Stefin B was shown to interact with amyloid-beta peptide of Alzheimer's disease in an oligomer specific manner, both in vitro and in the cells. It also has been shown that endogenous stefin B (with E at site 31) but especially the EPM1 mutant R68X and Y31-stefin B variant, and to a lesser extent EPM1 mutant G4R, are prone to form aggregates in cells.
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3.97Impact points
Intracellular aggregation of human stefin B: confocal and electron microscopy study.
Biology of the cell / under the auspices of the European Cell Biology Organization. 06/2010; 102(6):319-34.
Protein aggregation is a major contributor to the pathogenic mechanisms of human neurodegenerative diseases. Mutations in the CSTB (cystatin B) gene [StB (stefin B)] cause EPM1 (progressive myoclonus epilepsy of type 1), an epilepsy syndrome with features of neurodegeneration and increased oxidative... [more] Protein aggregation is a major contributor to the pathogenic mechanisms of human neurodegenerative diseases. Mutations in the CSTB (cystatin B) gene [StB (stefin B)] cause EPM1 (progressive myoclonus epilepsy of type 1), an epilepsy syndrome with features of neurodegeneration and increased oxidative stress. Oligomerization and aggregation of StB in mammalian cells have recently been reported. It has also been observed that StB is overexpressed after seizures and in certain neurodegenerative conditions, which could potentially lead to its aggregation. Human StB proved to be a good model system to study amyloid fibril formation in vitro and, as we show here, to study protein aggregation in cells. Endogenous human StB formed smaller, occasional cytoplasmic aggregates and chemical inhibition of the UPS (ubiquitin-proteasome system) led to an increase in the amount of the endogenous protein and also increased its aggregation. Further, we characterized both the untagged and T-Sapphire-tagged StB on overexpression in mammalian cells. Compared with wild-type StB, the EPM1 missense mutant (G4R), the aggregate-prone EPM1 mutant (R68X) and the Y31 StB variant (both tagged and untagged) formed larger cytosolic and often perinuclear aggregates accompanied by cytoskeletal reorganization. Non-homogeneous morphology of these large aggregates was revealed using TEM (transmission electron microscopy) with StB detected by immunogold labelling. StB-positive cytoplasmic aggregates were partially co-localized with ubiquitin, proteasome subunits S20 and S26 and components of microfilament and microtubular cytoskeleton using confocal microscopy. StB aggregates also co-localized with LC3 and the protein adaptor p62, markers of autophagy. Flow cytometry showed that protein aggregation was associated with reduced cell viability. We have shown that endogenous StB aggregates within cells, and that aggregation is increased upon protein overexpression or proteasome inhibition. From confocal and TEM analyses, we conclude that aggregates of StB show some of the molecular characteristics of aggresomes and may be eliminated from the cell by autophagy. Intracellular StB aggregation shows a negative correlation with cell survival.
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5.33Impact points
Stefin B interacts with histones and cathepsin L in the nucleus.
The Journal of biological chemistry. 03/2010; 285(13):10078-86.
Stefin B (cystatin B) is an endogenous inhibitor of cysteine proteinases localized in the nucleus and the cytosol. Loss-of-function mutations in the stefin B gene (CSTB) gene were reported in patients with Unverricht-Lundborg disease (EPM1). We have identified an interaction between stefin B and nuc... [more] Stefin B (cystatin B) is an endogenous inhibitor of cysteine proteinases localized in the nucleus and the cytosol. Loss-of-function mutations in the stefin B gene (CSTB) gene were reported in patients with Unverricht-Lundborg disease (EPM1). We have identified an interaction between stefin B and nucleosomes, specifically with histones H2A.Z, H2B, and H3. In synchronized T98G cells, stefin B co-immunoprecipitated with histone H3, predominantly in the G(1) phase of the cell cycle. Stefin B-deficient mouse embryonic fibroblasts entered S phase earlier than wild type mouse embryonic fibroblasts. In contrast, increased expression of stefin B in the nucleus delayed cell cycle progression in T98G cells. The delay in cell cycle progression was associated with the inhibition of cathepsin L in the nucleus, as judged from the decreased cleavage of the CUX1 transcription factor. In vitro, inhibition of cathepsin L by stefin B was potentiated in the presence of histones, whereas histones alone did not affect the cathepsin L activity. Interaction of stefin B with the Met-75 truncated form of cathepsin L in the nucleus was confirmed by fluorescence resonance energy transfer experiments in the living cells. Stefin B could thus play an important role in regulating the proteolytic activity of cathepsin L in the nucleus, protecting substrates such as transcription factors from its proteolytic processing.
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4.97Impact points
Protein conformational pathology in Alzheimer's and other neurodegenerative diseases; new targets for therapy.
Current Alzheimer research. 02/2010; 7(1):74-83.
The whole set of so-called >conformational< disorders, among them systemic amyloidoses, various dementias and other neurodegenerative diseases such as Parkinson's, Alzheimer's and amyotropic lateral sclerosis, may have similar molecular backgrounds: changes in protein conformation and ... [more] The whole set of so-called >conformational< disorders, among them systemic amyloidoses, various dementias and other neurodegenerative diseases such as Parkinson's, Alzheimer's and amyotropic lateral sclerosis, may have similar molecular backgrounds: changes in protein conformation and aggregation lead to toxic amyloid oligomers and fibrils. The so called aggresomes in eukaryotes (equivalent to inclusion bodies in prokaryotes), located at the centriole by the nucleus and composed of aggregated proteins, are believed to sequester the toxic material. They eventually get cleared from the cell by autophagy. When the cell defence system fails due to continuous production of a mutated protein or to other damage to the cell such as oxidative stress or protein modification as part of normal aging, familial or sporadic neurodegenerative diseases develop. Initially - for years - they are silent with no or mild symptoms. It could well be that aggregates represent a response to some other trigger or even a means of defence. However, the inherited cases with mutations leading to increased aggregation suggest the opposite to be the case. Evidence has accumulated that the soluble oligomers of amyloidogenic proteins are themselves cytotoxic and trigger a cascade of detrimental events in the cell, as summarized in the "amyloid cascade hypothesis". Among other plausible hypotheses for the mechanism of toxicity is the "channel hypothesis", which states that the soluble oligomers interact with cell membranes, causing influx of Ca2+ ions, which is an early sign of pathology and contributes to uncontrolled neurotransmission. Another factor are metal ions, such as Zn(2+), Cu(2+), Fe(3+), Al(3+), etc., leading to the "metal hypothesis". The delicate balance of metal ions in the brain is important to prevent oxidative stress, which can itself modify proteins and make them aggregation-prone. The advances in molecular and cellular studies will hopefully lead to novel therapies and eventually to a cure.
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5.33Impact points
Interaction between oligomers of stefin B and amyloid-beta in vitro and in cells.
The Journal of biological chemistry. 12/2009;
In order to contribute to the question of putative role of cystatins in Alzheimer's disease and in neuroprotection in general, we studied the interaction between human stefin B (cystatin B) and amyloid- beta(1-40) peptide (Abeta). Using surface plasmon resonance (SPR) and electrospray mass spect... [more] In order to contribute to the question of putative role of cystatins in Alzheimer's disease and in neuroprotection in general, we studied the interaction between human stefin B (cystatin B) and amyloid- beta(1-40) peptide (Abeta). Using surface plasmon resonance (SPR) and electrospray mass spectrometry (ESI MS) we were able to show a direct interaction between the two proteins. As an interesting new fact, we show that stefin B binding to Abetais oligomer specific. The dimers and tetramers of stefin B, which bind Abeta are domain-swapped as judged from structural studies. Consistent with the binding results, the same oligomers of stefin B inhibit Abetafibril formation. When expressed in cultured cells, stefin B co-localises with Abeta intracellular inclusions. It also co-immunoprecipitates with APP fragment containing the Abeta epitope. Thus, stefin B is another APP / Abetabinding protein in vitro and likely in cells.
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3.54Impact points
Essential role of Pro 74 in stefin B amyloid-fibril formation: dual action of cyclophilin A on the process.
FEBS letters. 05/2009; 583(7):1114-20.
We report that Pro74 in human stefin B is critical for fibril formation and that proline isomerization plays an important role. The stefin B P74S mutant did not fibrillate over the time of observation at 25 degrees C, and it exhibited a prolonged lag phase at 30 degrees C and 37 degrees C. The pepti... [more] We report that Pro74 in human stefin B is critical for fibril formation and that proline isomerization plays an important role. The stefin B P74S mutant did not fibrillate over the time of observation at 25 degrees C, and it exhibited a prolonged lag phase at 30 degrees C and 37 degrees C. The peptidyl prolyl cis/trans isomerase cyclophilin A, when added to the wild-type protein, exerted two effects: it prolonged the lag phase and increased the yield and length of the fibrils. Addition of the inactive cyclophilin A R55A variant still resulted in a prolonged lag phase but did not mediate the increase of the final fibril yield. These results demonstrate that peptidyl prolyl cis/trans isomerism is rate-limiting in stefin B fibril formation.
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5.13Impact points
The emerging role of cystatins in Alzheimer's disease.
BioEssays : news and reviews in molecular, cellular and developmental biology. 05/2009;
Recently opposing effects of cysteine protease inhibitors, the human cystatins, on neurodegeneration have been reported. Human cystatin C is a risk factor for late-onset Alzheimer's disease (AD), whereas human stefin B (cystatin B) has no direct involvement in AD. Conflicting data show that thei... [more] Recently opposing effects of cysteine protease inhibitors, the human cystatins, on neurodegeneration have been reported. Human cystatin C is a risk factor for late-onset Alzheimer's disease (AD), whereas human stefin B (cystatin B) has no direct involvement in AD. Conflicting data show that their target protease, cathepsin B, might be anti-amyloidogenic, helping in amyloid-beta (Abeta) clearance or, instead, might be involved in Abeta production. Some reports claim that cystatin C binds soluble Abeta, making transgenic animals healthier, others, in contrast, that deleting cystatins genes may contribute to amyloid pathology in animal models of AD.
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3.09Impact points
The mechanism of amyloid-fibril formation by stefin B: temperature and protein concentration dependence of the rates.
Proteins. 02/2009; 74(2):425-36.
Cystatins, a family of structurally related cysteine proteinase inhibitors, have proved to be useful model system to study amyloidogenesis. We have extended previous studies of the kinetics of amyloid-fibril formation by human stefin B (cystatin B) and some of its mutants, and proposed an improved m... [more] Cystatins, a family of structurally related cysteine proteinase inhibitors, have proved to be useful model system to study amyloidogenesis. We have extended previous studies of the kinetics of amyloid-fibril formation by human stefin B (cystatin B) and some of its mutants, and proposed an improved model for the reaction. Overall, the observed kinetics follow the nucleation and growth behavior observed for many other amyloidogenic proteins. The minimal kinetic scheme that best fits measurements of changes in CD and thioflavin T fluorescence as a function of protein concentration and temperature includes nucleation (modeled as N(I) irreversible transitions with equivalent rates (k(I)), which fitted with N(I) = 64), fibril growth and nonproductive oligomerization, best explained by an off-pathway state with a rate-limiting escape rate. Three energies of activation were derived from global fitting to the minimal kinetic scheme, and independently through the fitting of the individual component rates. Nucleation was found to be a first-order process within an oligomeric species with an enthalpy of activation of 55 +/- 4 kcal mol(-1). Fibril growth was a second-order process with an enthalpy of activation (27 +/- 5 kcal mol(-1)), which is indistinguishable from that of tetramer formation by cystatins, which involves limited conformational changes including proline trans to cis isomerization. The highest enthalpy of activation (95 +/- 5 kcal mol(-1) at 35 degrees C), characteristic of a substantial degree of unfolding as observed prior to domain-swapping reactions, equated with the escape rate of the off-pathway oligomeric state.
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2.12Impact points
Size and morphology of toxic oligomers of amyloidogenic proteins: a case study of human stefin B.
Amyloid : the international journal of experimental and clinical investigation : the official journal of the International Society of Amyloidosis. 09/2008; 15(3):147-59.
Amyloid-induced toxicity is a well-known phenomenon but the molecular background remains unclear. One hypothesis relates toxicity to amyloid-membrane interactions, predicting that amyloid oligomers make pores into membranes. Therefore, the toxicity and membrane interaction of prefibrillar aggregates... [more] Amyloid-induced toxicity is a well-known phenomenon but the molecular background remains unclear. One hypothesis relates toxicity to amyloid-membrane interactions, predicting that amyloid oligomers make pores into membranes. Therefore, the toxicity and membrane interaction of prefibrillar aggregates and individual oligomers of a non-pathological yet highly amyloidogenic protein human stefin B (cystatin B) was examined. By monitoring caspase-3 activity and by testing cell viability, we showed that the lag phase aggregates obtained at pH 5 and 3 were toxic to neuroblastoma cells. Of equal toxicity were the higher-order oligomers prepared at pH 7 by freeze-thaw cycles. The higher-order oligomers eluted on size-exclusion chromatography (SEC) as a broad peak comprising hexamers, octamers, 12- and 16-mers, well separated from monomers, dimers and tetramers. Only oligomers higher than the tetramers (Rh >3.5 nm) proved toxic, in contrast to dimers and tetramers. In accordance with data from SEC, dynamic light scattering and atomic force microscopy data indicate that the toxic oligomers have diameters larger than 4 nm. Critical pressure measurements showed that the toxic higher-order oligomers inserted more effectively into model lipid monolayers than dimers and tetramers. They also bound, similarly to prefibrillar aggregates, to the plasma membrane and became internalized. Taken together, our results confirm the importance of membrane interaction and perforation in the phenomenon of cytotoxicity.
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3.04Impact points
Interaction with model membranes and pore formation by human stefin B: studying the native and prefibrillar states.
The FEBS journal. 06/2008; 275(10):2455-66.
Human stefin B, from the family of cystatins, is used as a model amyloidogenic protein in studies of the mechanism of amyloid fibril formation and related cytotoxicity. Interaction of the protein's prefibrillar oligomers/aggregates with predominantly acidic phospholipid membranes is known to cor... [more] Human stefin B, from the family of cystatins, is used as a model amyloidogenic protein in studies of the mechanism of amyloid fibril formation and related cytotoxicity. Interaction of the protein's prefibrillar oligomers/aggregates with predominantly acidic phospholipid membranes is known to correlate with cellular toxicity. In the present study, we measured membrane interaction of the prefibrillar and native states for three variants: the Y31 isoform studied previously, the wild-type protein and the G4R mutant; the latter is observed in progressive myoclonus epilepsy of type 1. In addition to using critical pressure and surface plasmon resonance, we assessed membrane permeabilization by calcein release and electrophysiological measurements. It was demonstrated for the first time that wild-type stefin B and the Y31 isoform are able to form pores in planar lipid bilayers, whereas G4R destroys the bilayer by a non pore-forming process. Similarities to other amyloidogenic proteins and the possible physiological implications of our findings are discussed.
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3.87Impact points
Exclusion of the native alpha-helix from the amyloid fibrils of a mixed alpha/beta protein.
Journal of molecular biology. 02/2008; 375(2):487-98.
Members of the cystatin superfamily are involved in an inherited form of cerebral amyloid angiopathy and readily form amyloid fibrils in vitro. We have determined the structured core of human stefin B (cystatin B) amyloid fibrils using quenched hydrogen exchange and NMR. The core contains residues f... [more] Members of the cystatin superfamily are involved in an inherited form of cerebral amyloid angiopathy and readily form amyloid fibrils in vitro. We have determined the structured core of human stefin B (cystatin B) amyloid fibrils using quenched hydrogen exchange and NMR. The core contains residues from four of the five strands of the native beta-sheet, delimited by unprotected loop regions analogous to those of the native monomeric structure. However, non-native features are also apparent, the most striking of which is the exclusion of the native alpha-helix. Before forming amyloid in vitro, cystatins dimerise via 3D domain swapping, and assemble into tetramers with trans to cis isomerism of a conserved proline. In the fibril, the hinge loop that forms an extended beta-structure in the dimer remains protected, consistent with the domain-swapping interface being maintained. However, the fibril data are not compatible with a simple 3D domain-swapping model for amyloid formation, and the displacement of the helix points to alternative packing arrangements of native-like beta-structure, in which proline isomerism is important in preventing steric clashing.
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3.54Impact points
Similar toxicity of the oligomeric molten globule state and the prefibrillar oligomers.
FEBS letters. 02/2008; 582(2):203-9.
We report that a mutant of human stefin B is in a molten globule conformation. It has all the spectroscopic characteristics for such a state. We also demonstrate that the molten globule is oligomeric, eluting on SEC within a similar MW range than the higher order oligomers of the wild type protein, ... [more] We report that a mutant of human stefin B is in a molten globule conformation. It has all the spectroscopic characteristics for such a state. We also demonstrate that the molten globule is oligomeric, eluting on SEC within a similar MW range than the higher order oligomers of the wild type protein, which is confirmed by DLS and AFM. Both, the higher oligomers and the molten globule state bind ANS, implying a high degree of hydrophobic patches exposure and partial opening of the structure. Finally, we demonstrate that the oligomeric molten globule is as toxic as the prefibrillar aggregates obtained at acid pH or the higher order oligomers prepared at neutral pH.
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2.12Impact points
Amyloid fibril formation by human stefin B: influence of pH and TFE on fibril growth and morphology.
Amyloid : the international journal of experimental and clinical investigation : the official journal of the International Society of Amyloidosis. 10/2007; 14(3):237-47.
As shown before, human stefin B (cystatin B) populates two partly unfolded species, a native-like state at pH 4.8 and a structured molten globule state at pH 3.3 (high ionic strength), from each of which amyloid fibrils grow. Here, we show that the fibrils obtained at pH 3.3 differ from those at pH ... [more] As shown before, human stefin B (cystatin B) populates two partly unfolded species, a native-like state at pH 4.8 and a structured molten globule state at pH 3.3 (high ionic strength), from each of which amyloid fibrils grow. Here, we show that the fibrils obtained at pH 3.3 differ from those at pH 4.8 and that those obtained at pH 3.3 (protofibrils) do not transform readily to mature fibrils. In addition we show that amorphous aggregates are also a source of fibrils. The kinetics of amyloid fibril formation at different trifluoroethanol (TFE) concentrations were measured. TFE accelerates fibril growth at predenaturational concentrations of the alcohol. At concentrations higher than 10%, the fibrillar yield decreases proportionately as the population of an all alpha-helical, denatured form of the protein increases. At an optimum TFE concentration, the lag and the growth phases are observed, similarly to some other amyloidogenic proteins. Morphology of the protein species at the beginning and the end of the reactions was observed using atomic force microscopy and transmission electron microscopy. Final fibril morphologies differ depending on solvent conditions.
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3.87Impact points
Essential role of proline isomerization in stefin B tetramer formation.
Journal of molecular biology. 04/2007; 366(5):1569-79.
Here we present the tetrameric structure of stefin B, which is the result of a process by which two domain-swapped dimers of stefin B are transformed into tetramers. The transformation involves a previously unidentified process of extensive intermolecular contacts, termed hand shaking, which occurs ... [more] Here we present the tetrameric structure of stefin B, which is the result of a process by which two domain-swapped dimers of stefin B are transformed into tetramers. The transformation involves a previously unidentified process of extensive intermolecular contacts, termed hand shaking, which occurs concurrently with trans to cis isomerization of proline 74. This proline residue is widely conserved throughout the cystatin superfamily, a member of which, human cystatin C, is the key protein in cerebral amyloid angiopathy. These results are consistent with the hypothesis that isomerization of proline residues can play a decisive role in amyloidogenesis.
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2.71Impact points
A single prion protein peptide can elicit a panel of isoform specific monoclonal antibodies.
Peptides. 12/2006; 27(11):2695-705.
The main step in the pathogenesis of transmissible spongiform encephalopathies (TSE) is the conformational change of the normal cellular prion protein (PrP(C)) into the abnormal isoform, named prion (PrP(Sc)). Since PrP is a highly conserved protein, the production of monoclonal antibodies (mAbs) of... [more] The main step in the pathogenesis of transmissible spongiform encephalopathies (TSE) is the conformational change of the normal cellular prion protein (PrP(C)) into the abnormal isoform, named prion (PrP(Sc)). Since PrP is a highly conserved protein, the production of monoclonal antibodies (mAbs) of high specificity and affinity to PrP is a difficult task. In the present study we show that it is possible to overcome the unresponsiveness of the immune system by immunizing wild-type BALB/c mice with a 13 amino acid PrP peptide from the C-terminal part of PrP, bound to the keyhole limpet hemocyanin (KLH). Immunization induced predominantly anti-PrP(Sc) humoral immune response. Furthermore, we were able to obtain a panel of mAbs of IgG class specific for different non-self-conformations of PrP, with anti-PrP(Sc)-specific mAbs being the most abundant.
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3.04Impact points
High affinity copper binding by stefin B (cystatin B) and its role in the inhibition of amyloid fibrillation.
The FEBS journal. 10/2006; 273(18):4250-63.
We show that human stefin B, a protease inhibitor from the family of cystatins, is a copper binding protein, unlike stefin A. We have used isothermal titration calorimetry to directly monitor the binding event at pH 7 and pH 5. At pH 7 stefin B shows a picomolar affinity for copper but at pH 5 the a... [more] We show that human stefin B, a protease inhibitor from the family of cystatins, is a copper binding protein, unlike stefin A. We have used isothermal titration calorimetry to directly monitor the binding event at pH 7 and pH 5. At pH 7 stefin B shows a picomolar affinity for copper but at pH 5 the affinity is in the nanomolar range. There is no difference in the affinity of copper between the wildtype stefin B (E31 isoform) and a variant (Y31 isoform), whereas the mutant (P79S), which is tetrameric, does not bind copper. The conformation of stefin B remains unaltered by copper binding. It is known that below pH 5 stefin B undergoes a conformational change and amyloid fibril formation. We show that copper binding inhibits the amyloid fibril formation and, to a lesser degree, the initial aggregation. Similarities to and differences from other copper binding amyloidogenic proteins are discussed.
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3.09Impact points
Folding and amyloid-fibril formation for a series of human stefins' chimeras: any correlation?
Proteins. 03/2006; 62(4):918-27.
To study the influence of whole secondary structure elements to the process of folding and amyloid-fibril formation, chimeras of stefins have been prepared. GdnHCl denaturation curves and folding rates (chevron plots) have been analyzed based on a two-state mechanism. The order of stability is: stef... [more] To study the influence of whole secondary structure elements to the process of folding and amyloid-fibril formation, chimeras of stefins have been prepared. GdnHCl denaturation curves and folding rates (chevron plots) have been analyzed based on a two-state mechanism. The order of stability is: stefin A > aAbbbb > bAbbbb > stefin B = aBaaaa > bBaaaa, where the make up of chimeric proteins is designated by small letters representing the source of individual strands (a for stefin A, b for stefin B) and a capital letter representing the source of the helix (A for stefin A and B for stefin B). Only the fast folding reactions were included in the analysis and it has been found that stefin B folds the fastest (657 s(-1)). Similarly, fast folders are the chimeric proteins aBaaaa and bBaaaa, both of which contain the alpha-helix of stefin B. Unfolding rates correlate very well with protein stability, with the slowest rate for the most stable protein, stefin A. Amyloid-fibril growth was measured for each protein by monitoring thioflavin T fluorescence and was visualized using electron microscopy. The propensity to form amyloid-fibrils is in the order: stefin B > bAbbbb > aAbbbb > bBaaaa > aBaaaa > stefin A. This order does not correlate with stability, or with the folding or unfolding rates. Instead, the propensity to fibrillize is related to selected parts of structure, such as the beta-sheet of stefin B, and can be predicted reasonably well by calculating the beta-strand propensity of the denatured states.
Following (40)
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Tam Phuong
SKKU, School of medicine -
Sandeep Kumar Singh
Banaras Hindu University -
Dirk Linke
Max Planck Insitute for Developmental Biology -
PHANI MOHAN KRISHNA
ANAGHA DATTA TRADE -
Stephanie Cadot
University of Sussex
