ELASTASE INHIBITION BY THE C-TERMINAL DOMAINS OF ALPHA-CRYSTALLIN ANDSMALL HEAT-SHOCK PROTEIN

alpha-Crystallin, an abundant eye-lens protein and a stress protein in other tissues, shows structural and functional similarities with the small heat-shock proteins. One of the properties in common is the inhi bition of elastase. We now report that the separated subunits of alpha -crystallin, alpha A and alpha B, also exhibit elastase inhibition, wh ereas phosphorylation of these subunits apparently has no influence on the inhibitory capacity. Furthermore, for both alpha A-crystallin and mouse HSP25 the putative C-terminal structural domain, comprising the major region of homology between these proteins, is sufficient to giv e elastase inhibition. With database search no homology could be found between the three proteins under investigation and any of the known c onsensus sequences of proteinase inhibitor families.