THE PROTEIN-FOLDING ACTIVITY OF CHAPERONINS CORRELATES WITH THE SYMMETRICAL GROEL(14)(GROES(7))(2) HETEROOLIGOMER

Chaperonins GroEL and GroES form, in the presence of ATP, two types of heterooligomers in solution: an asymmetric GroEL(14)GroES(7) ''bullet ''-shaped particle and a symmetric GroEL(14)(GroES(7))(2) ''football'' -Shaped particle. Under limiting concentrations of ATP or GroES, exces s ADP, or in the presence of 5'-adenylyl imidodiphosphate, a correlati on is seen between protein folding and the amount of symmetric GroEL(1 4)(GroES(7))(2) particles in a chaperonin solution, as detected by ele ctron microscopy or by chemical crosslinking. kinetic analysis suggest s that protein folding is more efficient when carried out by a chapero nin solution populated with a majority of symmetric GroEL(14)(GroES(7) )(2) particles than by a majority of asymmetric GroEL(14)GroES(7) part icles. The symmetric heterooligomer behaves as a highly efficient inte rmediate of the chaperonin protein folding cycle in vitro.