Interactive domains for chaperone activity in the small heat shock protein, human crystallin

Protein pin arrays identified seven interactive sequences for chaperone activity in human alpha B crystallin using natural lens proteins, beta(H) crystallin and gamma D crystallin, and in vitro chaperone target proteins, alcohol dehydrogenase and citrate synthase. The N-terminal domain contained two interactive sequences, 9WIRRPFFPFHSP20 and (43)SLSPFYLRPPSFLRAP(58). The alpha crystallin core domain contained four interactive sequences, 75FSVNLDVK82 (beta 3), 113FISREFHR120, 131LTITSSLS138 (beta 8), and (141)GVLTVNGP(148) (beta 9). The C-terminal domain contained one interactive sequence, 157RTIPITRE164, that included the highly conserved I-X-IN motif. Two interactive sequences, 73DRFSVNLDVKHFS85 and (131)LTITSSLSDGV(141), belonging to the alpha crystallin core domain were synthesized as peptides and assayed for chaperone activity in vitro. Both synthesized peptides inhibited the thermal aggregation of beta(H) crystallin, alcohol dehydrogenase, and citrate synthase in vitro. Five of the seven chaperone sequences identified by the pin arrays overlapped with sequences identified previously as sequences for subunit-subunit interactions in human alpha B crystallin. The results suggested that interactive sequences in human alpha B crystallin have dual roles in subunit-subunit assembly and chaperone activity.