New Physiological Function of Chaperones, Facilitating Reconstitution of Apoenzymes

Abstract

One of the important branches of modern biochemistry and molecular biology is the investigation of structure and function of molecular chaperones. The main function of the family of molecular chaperones named as small heat shock proteins (sHsps) is suppression of aggregation of non-native protein species formed under stress conditions or during folding of the newly synthesized polypeptide chains [1-3]. The low molecular mass of monomers (from 12 to 43 kDa) and tendency to form large oligomers with high molecular masses up to 1000 kDa are typical of this protein family [4-14]. The presence of a conservative α-crystallin domain in the structure of sHsp seems to be important for the formation of stable dimers, whereas variable N- and C-terminal ends seem to participate in the formation of large oligomers [2-4,7]. It is supposed that the polydispersity and quaternary structure dynamics play an important role in cellular sHsp chaperones function [2,12]. sHsps cannot provide folding of the polypeptide chain; however, they form complexes with non-native proteins and can transfer the latter either to ATP-dependent chaperones that provide assistance to protein folding or proteasomes, where proteolytic degradation of the unfolded proteins occurs [15-19]