The pivotal role of the beta 7 strand in the intersubunit contacts of different human small heat shock proteins.

Mymrikov EV; Bukach OV; Seit-Nebi AS; Gusev NB

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Article

Title:	The pivotal role of the beta 7 strand in the intersubunit contacts of different human small heat shock proteins.
Authors:	Mymrikov EV; Bukach OV; Seit-Nebi AS; Gusev NB
Publication:	Cell Stress Chaperones. 2010 Jul;15(4):365-77. doi: 10.1007/s12192-009-0151-8. Epub 2009 Oct 24.
PubmedID	19856132
Abstract
Human alpha B-crystallin and small heat shock proteins HspB6 and HspB8 were mutated so that all endogenous Cys residues were replaced by Ser and the single Cys residue was inserted in a position homologous to that of Cys137 of human HspB1, i.e. in a position presumably located in the central part of beta 7 strand of the alpha-crystallin domain. The secondary, tertiary, and quaternary structures of thus obtained Cys-mutants as well as their chaperone-like activity were similar to those of their wild-type counterparts. Mild oxidation of Cys-mutants leads to formation of disulfide bond crosslinking neighboring monomers thus indicating participation of the beta 7 strand in intersubunit interaction. Oxidation weakly affects the secondary and tertiary structure, does not affect the quaternary structure of alpha B-crystallin and HspB6, and shifts equilibrium between monomer and dimer of HspB8 towards dimer formation. It is concluded that the beta 7 strand participates in the intersubunit interaction of four human small heat shock proteins (alpha B-crystallin, HspB1, HspB6, HspB8) having different structure of beta2 strand of alpha-crystallin domain and different length and composition of variable N- and C-terminal tails.