THE FORMATION OF SYMMETRICAL GROEL-GROES COMPLEXES IN THE PRESENCE OFATP

The incubation of chaperonins cpn60 (GroEL) and cpn10 (GroES) from E. coli in the presence of Mg-ATP and KCl generates the formation, as rev ealed by electron microscopy, of GroEL-GroES complexes with a symmetri cal shape in which one toroidal GroES oligomer is bound to each end of the tetradecameric GroEL aggregate (1:2 GroEL:GroES oligomer molar ra tio). The symmetrical complexes are not observed in the presence of AD P or the non-hydrolyzable ATP analog, ATP gamma S, where only asymmetr ical complexes (1:1 GroEL:GroES oligomer molar ratio) are formed. Thes e results suggest that ATP hydrolysis is required for the formation of symmetrical complexes.