Maintenance of chaperone-like activity despite mutations in a conserved region of murine lens alpha B crystallin

PURPOSE: To understand the relationship between certain conserved residues in alpha B crystallin and the chaperone-like function of the protein. METHODS: In alpha B crystallin, residues H101 to R120 are highly conserved between alpha B crystallin and alpha A crystallin (85% identity), and betwe en alpha B crystallin and the small heat shock protein hsp 27 (80% identity ). We made three substitution mutants of alpha B crystallin: the single mut ant F118A, and the double mutants K103L/H104I, and E110H/H111E. RESULTS: Polyacrylamide gel electrophoresis revealed no decrease in aggrega te size or measureable structural changes between them and the native struc ture. Using the insulin aggregation assay, all three mutants had identical chaperone-like activity to the wild-type recombinant alpha B crystallin. CONCLUSIONS: Despite the high conservation in this area of sequence between alpha B crystallin, alpha A crystallin, and the small heat shock protein h sp 27, mutations F118A, K103L/H104I, and E110H/H111E did not significantly alter chaperone-like activity.