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|Title:||The influence of the N-terminal region proximal to the core domain on the assembly and chaperone activity of αB-crystallin|
Andrew Aquilina, J.
|Citation:||Cell Stress and Chaperones, 2018; 23(5):827-836|
|Blagojce Jovcevski, J. Andrew Aquilina, Justin L.P. Benesch, Heath Ecroyd|
|Abstract:||αB-Crystallin (HSPB5) is a small heat-shock protein that is composed of dimers that then assemble into a polydisperse ensemble of oligomers. Oligomerisation is mediated by heterologous interactions between the C-terminal tail of one dimer and the core "α-crystallin" domain of another and stabilised by interactions made by the N-terminal region. Comparatively little is known about the latter contribution, but previous studies have suggested that residues in the region 54-60 form contacts that stabilise the assembly. We have generated mutations in this region (P58A, S59A, S59K, R56S/S59R and an inversion of residues 54-60) to examine their impact on oligomerisation and chaperone activity in vitro. By using native mass spectrometry, we found that all the αB-crystallin mutants were assembly competent, populating similar oligomeric distributions to wild-type, ranging from 16-mers to 30-mers. However, circular dichroism spectroscopy, intrinsic tryptophan and bis-ANS fluorescence studies demonstrated that the secondary structure differs to wild type, the 54-60 inversion mutation having the greatest impact. All the mutants exhibited a dramatic decrease in exposed hydrophobicity. We also found that the mutants in general were equally active as the wild-type protein in inhibiting the amorphous aggregation of insulin and seeded amyloid fibrillation of α-synuclein in vitro, except for the 54-60 inversion mutant, which was significantly less effective at inhibiting insulin aggregation. Our data indicate that alterations in the part of the N-terminal region proximal to the core domain do not drastically affect the oligomerisation of αB-crystallin, reinforcing the robustness of αB-crystallin in functioning as a molecular chaperone.|
|Keywords:||Proteostasis; molecular chaperone; small heat-shock protein; native mass spectrometry; protein aggregation; αB-crystallin; HSPB5; amyloid fibrils|
|Rights:||© Cell Stress Society International 2018|
|Appears in Collections:||Biochemistry publications|
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