EXPRESSION OF RECOMBINANT ALPHA-A(INS)-CRYSTALLIN AND NOT ALPHA-A-CRYSTALLIN INHIBITS BACTERIAL-GROWTH

alpha A-Crystallin and alpha A(ins)-crystallin are derived from the al pha A-crystallin gene via alternative splicing. They are identical exc ept for the presence of a polypeptide, 23 amino acids long, encoded by the 'insert' exon, Evolutionary logic would suggest that the insertio n of a 23 amino acid peptide in the middle of alpha A-crystallin, a pr otein evolving more slowly than either histone H1, cytochrome c or hem oglobin, would lead to appreciable structural and functional changes, However, based on physico-chemical studies, it is presently believed t hat alpha A-crystallin and alpha A(ins)-crystallin are functionally eq uivalent and that the presence of the 'insert' peptide in alpha A(ins) -crystallin is inconsequential. We report here that the independent ex pression of recombinant alpha A(ins) crystallin, and not alpha A-cryst allin, inhibits growth of the bacterial host. These observations were confirmed in coexpression experiments, wherein both the proteins were expressed in the same cell, Interestingly, growth inhibition is revers ible, Importantly, the data demonstrate that it is catalytic amounts a nd not the gross accumulation of alpha A(ins)-crystallin which causes growth inhibition, Given the prior knowledge that alpha A-crystallin a nd alpha A(ins)-crystallin differ by a peptide of 23 amino acids, thes e data suggest that the 'insert peptide' in alpha A(ins)-crystallin im parts properties on this protein that are different from alpha A-cryst allin.