DIFFERENTIAL-EFFECTS OF MOLECULAR CHAPERONES ON REFOLDING OF HOMOLOGOUS PROTEINS

Three homologous aspartate aminotransferases with virtually identical spatial structures and pairwise amino acid sequence identities of >40% differ markedly with respect to the yield of renaturation upon diluti on from 6 M guanidine hydrochloride (mitochondrial << cytosolic < Esch erichia coli. The enzymes also respond differently to molecular chaper ones. GroEL/ GroES, the Hsp60 homolog of E. coli, increased considerab ly the yield of renaturation of mitochondrial aspartate aminotransfera se and to a lesser extent that of its cytosolic counterpart, but not t hat of the E. coli enzyme, DnaK/DnaJ/GrpE, the Hsp70 system of E. coli , also increased the yield of renaturation of mitochondrial aspartate aminotransferase. Apparently, specific features in the amino acid sequ ence or the folding pathway which are independent of the final seconda ry and tertiary structure determine the interactions of the folding pr oteins with the chaperone systems.