Characteristics of super alpha A-crystallin, a product of in vitro exon shuffling

alpha A-Crystallin, a small heat shock protein with chaperone-like activity , forms dynamic multimeric complexes, Recently we described the spontaneous generation of a mutant protein (super alpha A-crystallin) by exon duplicat ion arisen via exon shuffling confirming a classic hypothesis by Gilbert [N ature 271 (1978) 501]. Comparison of super alpha A-crystallin, which is via ble in a mouse skeletal muscle cell line, with normal alpha A-crystallin sh ows that it has diminished thermostability, increased exposure of hydrophob ic patches, a larger complex size and lost its chaperone activity. However, super alpha A-crystallin subunits exchange as readily between complexes as does normal alpha A-crystallin, These data indicate that chaperone-like ac tivity may vanish independent of subunit hydrophobicity and exchangeability . (C) 2000 Federation of European Biochemical Societies. Published by Elsev ier Science B.V. All rights reserved.