Self-complementary motifs (SCM) in α-crystallin small heat shock proteins

Small heat shock proteins (sHsp) have been implicated in many cell processes involving the dynamics of protein-protein interactions. Two unusual sequences containing self-complementary motifs (SCM) have been identified within the conserved alpha-crystallin domain of sHsps. When two SCMs are aligned in an anti-parallel direction (N to C and C to N), the charged or polar residues form either salt bridges or hydrogen bonds while the non-polar residues participate in hydrophobic interactions. When aligned in reverse order, the residues of these motifs in alpha-crystallin subunits form either hydrophobic and/or polar interactions. Homology based molecular modeling of the C-terminal domain of cr-crystallin subunits using the crystal structure of MjHSP16.5 suggests that SCM1 and 2 participate in stabilizing secondary structure and subunit interactions. Also there is overwhelming evidence that these motifs are important in the chaperone-like activity of alpha-crystallin subunits. These sequences are conserved and appear to be characteristic of the entire sHsp superfamily, Similar motifs are also present in the Hsp70 family and the immunoglobulin superfamily. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.