EVIDENCE FOR A LIPOCHAPERONIN - ASSOCIATION OF ACTIVE PROTEIN-FOLDINGGROESL OLIGOMERS WITH LIPIDS CAN STABILIZE MEMBRANES UNDER HEAT-SHOCKCONDITIONS

During heat shock, structural changes in proteins and membranes may le ad to cell death, While GroE and other chaperone proteins are involved ill the prevention of stress-induced protein aggregation and in the r ecovery of protein structures, a mechanism for short-term membrane sta bilization during stress remains to be established, We found that GroE L chaperonin can associate with model lipid membranes, Binding was app arently governed by the composition and the physical state of the host bilayer. Limited proteolysis of GroEL oligomers by proteinase K, whic h removes selectively the conserved glycine- and methionine-rich C ter minus, leaving the chaperonin oligomer intact, prevented chaperonin as sociation with lipid membranes, GroEL increased the lipid order in the liquid crystalline state, yet remained functional as a protein-foldin g chaperonin, This suggests that, during stress, chaperonins can assum e the functions of assisting the folding of both soluble and membrane- associated proteins while concomitantly stabilizing lipid membranes.