BACTERIOPHAGE-T4 ENCODES A CO-CHAPERONIN THAT CAN SUBSTITUTE FOR ESCHERICHIA-COLI GROES IN PROTEIN-FOLDING

SEVERAL bacteriophages use the Escherichia coli GroES and GroEL chaper onins for folding and assembly of their morphogenetic structures1. Bac teriophage T4 is unusual in that it encodes a specialized protein (Gp3 1) that is thought to interact with the host GroEL and to be absolutel y required for the correct assembly of the major capsid protein (Gp23) in vivo2-4. Here we show that despite the absence of amino-acid seque nce similarity between Gp31 and GroES5,6 Gp31 can functionally substit ute for the GroES co-chaperonin in the morphogenesis of bacteriophages lambda and T5, the in vivo and in vitro chaperonin-dependent assembly of ribulose bisphosphate carboxylase (Rubisco), as well as overall ba cterial growth at the non-permissive temperature. Like GroES, the bact eriophage Gp31 protein forms a stable complex with the E. coli GroEL p rotein in the presence of Mg-ATP and inhibits the ATPase activity of G roEL in vitro.