Interaction and biophysical properties of human lens Q155*βB2-crystallin mutant

PURPOSE: Missense mutations in crystallin genes have been identified in autosomal dominant congenital cataracts. A truncation in the CRYBB2 gene (Q155*) has been associated with cerulean cataract, however its effects on biophysical properties have not been reported. We sought to determine the changes in conformation and protein-protein interactions brought about by this mutation. METHODS: Site specific mutations were performed to obtain the Q155* beta B2-crystallin mutant. Protein-protein interactions were screened by a mammalian two-hybrid system assay. Conformational changes were studied with spectroscopy (circular dichroism and fluorescence) and FPLC chromatography. RESULTS: We detected a decrease in protein-protein interactions for the Q155* beta B2-crystallin mutant. The Q155* mutant shows decreased ordered structure and stability but the partially unfolded protein retains some dimer structure. CONCLUSIONS: The Q155* mutation in beta B2-crystallin causes changes in biophysical properties that might contribute to cataract formation.