Dissociation is not required for alpha-crystallin's chaperone function.

Bovine alpha-crystallin was crosslinked with glutaraldehyde under conditions designed to minimise intermolecular reactions. The crosslinked protein was too large to enter SDS polyacrylamide gels but HPLC-gel permeation chromatography revealed that the Stoke's radii of the native and crosslinked proteins were very similar. These observations indicate that only intramolecular crosslinks had formed and that the crosslinked protein could not dissociate to smaller species. The crosslinked alpha-crystallin was able to inhibit the thermally-induced precipitation of beta-crystallin and appeared to be more effective than the native protein under the same conditions. It is concluded that the chaperone activity of alpha-crystallin is a surface phenomenon and dissociation into smaller species is not required.