Purification of a heat-stable beta-crystallin polypeptide of the bovine lens

A major polypeptide component of bovine lens beta-crystallins has been found to be heat stable. This property is utilized for purification of this polypeptide on a preparative scale. A homogenate of lens crystallins buffered at pH of 7.3 with 0.95 M Tris containing 1mM DTT and 1mM EDTA is heated to 97-99 degrees C for 3-5 min. Denatured proteins are removed and the clear supernatant is lyophilized. The lyophilized material mostly consists of the major polypeptide component common to the beta-crystallins with minor quantities of some low molecular weight polypeptides. These contaminants can be removed by preparative polyacrylamide gel electrophoresis. Amino acid analysis, electrophoretic mobility and chromatographic behavior of the purified polypeptide indicate that it is similar to the beta Bp polypeptide. Antibodies raised against this polypeptide react with all beta-crystallins but not with the alpha-or gamma crystallins.