STRUCTURAL STUDIES ON BETA-H-CRYSTALLIN FROM BOVINE EYE LENS

Bovine lens βH-crystallin, isolated at pH 6·7, undergoes reversible dissociation into dimers and an intermediate size of oligomer (peak A) at pH 5·4. Peak A is enriched in the βB1 subunit but lacks βB2, whereas βB2 is a major component of the dimers. A method for isolation of βB1 from peak A is described. The pH dependence of the dissociation-reassociation suggests that histidines on the surface of the dimers become buried in the assembly of βH-crystallin. The positions of the four histidines on the surface of the compact domains of each subunit of the βB2 homodimer are shown. The βB1-enriched oligomer has a much lower solubility compared with the βB2 containing βH-crystallin. It is possible that βB2 plays a role in solubilizing β-crystallin aggregates. © 1992.