INFLUENCE OF THE GROE MOLECULAR CHAPERONE MACHINE ON THE IN-VITRO REFOLDING OF ESCHERICHIA-COLI BETA-GALACTOSIDASE

We have studied the effect of the components of the GroE molecular cha perone machine on the refolding of the Escherichia coli enzyme beta-ga lactosidase, a tetrameric protein whose 116-kDa protomers should not c ompletely fit within the central cavity of the GroEL toroid. In the ab sence of other additives, GroEL formed a weak complex with chemically denatured beta-galactosidase, reduced its propensity to aggregate, and increased the recovery yields of active enzyme twofold without alteri ng its folding pathway. When present together with the chaperonin, ATP - and to a lesser extent AMP-PNP - reduced the recovery yields and le d to the resumption of aggregation. The use of the complete chaperonin system (GroEL, GroES, acid ATP) eliminated the GroEL-mediated increas e in recovery and folding proceeded less efficiently than in buffer al one. This unusual behavior can be explained in terms of a chaperonin ' 'buffering'' effect and the different affinities of GroE complexes for denatured beta-galactosidase.