Abstract
Correct assembly of the heads of bacteriophages .lambda. and T4 requires the function of the groE gene of the E. coli host. A transducing derivative of .lambda., called .lambda.gt-Ec .cntdot. groE, that carries a functional copy of the groE gene was isolated. Unlike wild-type .lambda., this phage can form plaques on hosts with a mutant groE gene. An amber mutation in the groE gene carried by the phage was isolated, and this identified the groE product as a protein of MW 65,000. In the phage, the groE gene is under the control of an early phage promoter.