Abstract
HspB1 is a mammalian sHsp that is ubiquitously expressed in almost all tissues and involved in regulating many vital functions. Although the recent crystal structure of human HspB1 showed that 24 monomers form the oligomeric complex of human HspB1 in a spherical configuration, the molecular architecture of HspB1 is still controversial. In this study, we examined the oligomeric structural change of CgHspB1 by sedimentation velocity analytical ultracentrifugation. At the low temperature of 4 °C, CgHspB1 exists as an 18-mer, probably a trimeric complex of hexamers. It is relatively unstable and partially dissociates into small oligomers, hexamers, and dodecamers. At elevated temperatures, the 24-mer was more stable than the 18-mer. The 24-mer is also in dynamic equilibrium with the dissociated oligomers in the hexameric unit. The hexamer further dissociates to dimers. The disulfide bond between conserved cysteine residues seems to be partly responsible for the stabilization of hexamers. The N-terminal domain is involved in the assembly of dimers and the interaction between hexamers. It is plausible that CgHspB1 expresses a chaperone function in the 24-mer structure.
Highlights
Small heat shock proteins are members of molecular chaperones present in all kingdoms of life [1]
This study examined the oligomeric structural change of CgHspB1 by sedimentation velocity analytical ultracentrifugation (SV-AUC)
We found that it was not easy to analyze the dissociated structures of CgHspB1 by size-exclusion chromatography (SEC) due to the interaction with the column
Summary
Small heat shock proteins (sHsps) are members of molecular chaperones present in all kingdoms of life [1]. They protect cells from damage under various stress conditions. Mutations in human sHsps result in multiple diseases, myopathies, neuropathies, and cataracts [2]. SHsps bind to partially folded or denatured proteins, preventing irreversible aggregation or promoting correct substrate folding. SHsps share a highly conserved α-crystallin domain (ACD) flanked by the N-terminal domain (NTD) and Cterminal extension (CTE) [1]. Motif, which plays an essential role in oligomerization [3]. The NTD plays a driving role in oligomer formation and interactions with substrate proteins
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