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- Aisenbrey, Christopher, et al.
(författare)
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SOD1 associates to membranes in its folded apo-state
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Annan publikation (populärvet., debatt m.m.)abstract
- Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease accompanied by misfolding and intracellular deposition of superoxide dismutase 1 (SOD1). Although the molecular details behind this misfolding process are yet poorly understood, increasing evidence suggest that SOD1 is most susceptible to misfolding in its metal-free and relatively unstable apo-state. Here, we addressed the question, if misfolding and aggregation of SOD1 involves erroneous interactions with membranes as has been implicated for the Aβ peptide in Alzheimers disease. To examine this possibility we subjected various apo SOD1 variants to the presence of different membrane systems. The results reveal that wild type apoSOD1 but to less extent destabilized ALS mutations interact with charged vesicles under physiologically relevant conditions, thereby acquiring pronounced helical structural features. As the data further show, the protein binds to the membranes by an electrostatically driven mechanism, which requires a folded apo-state conformation and a negative membrane surface potential. Unfolded SOD1 molecules show no appreciable affinity to the membrane surfaces yielding a correlation between increased stability, i. e. occupancy of folded molecules and extend of membrane association. Since this trend opposes the correlation between decreased SOD1 stability and progression of neural damage, the results suggest that membrane association is not part of the ALS mechanism. An explanation could be that the observed membrane association of apo SOD1 is reversible and does not ‘bleed out’ in irreversible aggregation as observed for other precursors of protein-misfolding diseases.
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- Bugaytsova, Jeanna, et al.
(författare)
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pH regulated H. pylori adherence : implications for persistent infection and disease
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Helicobacter pylori’s BabA adhesin binds strongly to gastric mucosal ABH/Leb glycans on the stomach epithelium and overlying mucus, materials continuously shed into the acidic gastric lumen. Here we report that this binding is acid labile, acid inactivation is fully reversible; and acid lability profiles vary with BabA sequence and correlate with disease patterns. Isogenic H. pylori strains from the gastric antrum and more acidic corpus were identified that differed in acid lability of receptor binding and in sequence near BabA’s carbohydrate binding domain. We propose that reversible acid inactivation of receptor binding helps H. pylori avoid clearance by mucosal shedding, and that strain differences in acid lability affect tissue tropism and the spectrum of associated gastric diseases.
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- Byström, Roberth, 1971-, et al.
(författare)
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Electrostatic interactions between negatively charged phospolipid membranes and SOD1 protein : Effect of charge changing fALS mutations
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Annan publikation (populärvet., debatt m.m.)abstract
- The neurodegenerative disease amyotrophic lateral sclerosis (ALS) is closely connected to single site mutations of the Cu/Zn superoxide dismutase (SOD1) protein, whose pathological conversion into misfolded aggregates is a hallmark of ALS. To explore the impact of protein net charge changing ALS relevant SOD1 mutations on their ability to interact with neuronal membranes and the consequences for their folding behaviour, we studied by circular dichroism the conformational changes of the SOD1pWT, SOD1N86D and SOD1N86K species in their apo-state in the presence of increasing amounts of negatively charged lipid bilayers.. The results clearly indicate an electrostatically driven association process, where the association event induces a pronounced increase in the helical character of the pWT and the N86D species, characterized by long patient survival times. To the opposite, the charge reducing N86K mutation shows more pronounced β-like features in the presence of membranes in comparison to the other two species; an observation which most likely reflects its reduced stability in its apo-state in combination with a very fast ALS progression.
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- Byström, Roberth, 1971-, et al.
(författare)
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Identification of property outliers among ALS-associated SOD1 mutations : Common effect on surface hydrogen bonds
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Annan publikation (populärvet., debatt m.m.)abstract
- In good accord with the protein-aggregation hypothesis for neurodegenerative diseaseALS-associated SOD1 mutations are found to reduce structural stability or netrepulsive charge. Moreover there are weak indications that the ALS diseaseprogression is correlated with the degree of mutational impact on the SOD1 structure.A bottleneck for obtaining more conclusive information about these structure-diseaserelationships, however, is the large intrinsic variability in patient survival times andinsufficient disease statistics for the majority of ALS-provoking mutations. As analternative test of the structure-disease relationship we focus here on the SOD1 amutation that appears to be outliers in the data set. The results identify several ALSprovokingmutations whose only effect on apo SOD1 is the elimination orintroduction of a single charge, i.e., D76V/Y, D101N and N139D/K. Thethermodynamic stability and folding behaviour of these mutants are indistinguishablefrom the wildtype control, showing that structurally benign replacements of individualsurface charges are sufficient to trigger ALS. Moreover, D101N is a clear outlier inthe plot of stability loss vs. patient survival time by having too rapid diseaseprogression. Common to the identified mutations is that they truncate conserved saltlinksand/or H-bond networks in the functional loops IV or VII. The results show thatthe local impact of ALS-associated mutations on the SOD1 molecule can sometimesoverrun their global effects on stability and net repulsive charge, and point at theanalysis of property outliers as an efficient strategy for mapping out new ALSprovokingfeatures.
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