ROLE OF HSP70 SUBFAMILY, SSA, IN PROTEIN-FOLDING IN YEAST-CELLS, SEENIN LUCIFERASE-TRANSFORMED SSA MUTANTS

To investigate the role of constitutive hsp70 in protein folding and t o probe tile supplementation by other hsps in this folding, yeast tell s espressing reduced constitutive hsp70 proteins, ssa1ssa2, were trans formed with a plasmid espressing a bacterial luciferase protein. With several independent clone cells of transformants, the levels of lucife rase activity and some hsps, such as hsp104, hsp90, hsp70 and hsp26, w ere examined, The luciferase activity mas significantly lower in ssa1s sa2 transformants than in the wild type (wt) cell transformed with the same plasmid. Among several clone cells of ssa1ssa2, the cells with h igher luciferase activities exhibited higher amounts of Ssa4 which is known to be expressed instead a lacking Ssa1 and Ssa2. The luciferase activity closely correlated with the amount of Ssa proteins, mere than with the amount of other hsps, It is suggested that constitutional Ss a ''chaperones'' are needed for the folding of proteins and, in cells lacking Ssa1 and Ssa2 the increased Ssa4 is thought to partly compensa te for their role irt the folding of luciferase in vivo.