Cloning, High Level Expression and Purification of Rat betaB2-crystallin

beta-crystallins are the largest group of lens structural proteins, which are necessary for both the high refractive index and the transparency of the eye lens, and have been implicated in various kinds of cataracts. To obtain abundant betaB2-crystallin for the study of the mechanism of their oligomerization, a bacterial expression system for betaB2-crystallin and a rapid method for its purification were developed. cDNA encoding rat betaB2-crystallin was cloned using RT-PCR. After the induction of recA promoter with nalidixic acid, abundant protein was produced in E. coli. betaB2-crystallin comprised about 30% of the total bacterial proteins and it is water-soluble. After anion-exchange chromatography on DEAE cellulose and gel filtration on Sephadex G-100, the protein was obtained pure as judged by SDS-PAGE. The high level expression and rapid purification of recombinant betaB2-crystallin will facilitate the further study of structure-function relationship of betaB2-crystallin.