Genetic analysis of bacteriophage-encoded cochaperonins

Early genetic studies identified the Escherichia coli groES and groEL genes because mutations in them blocked the growth of bacteriophages lambda and T4. Subsequent genetic and biochemical analyses have shown that GroES and G roEL constitute a chaperonin machine, absolutely essential for E, coli grow th, because it is needed for the correct folding of many of its proteins. I n spite of very little sequence identity to GroES, the bacteriophage T4-enc oded Gp31 protein and the bacteriophage RB49-encoded CocO protein are bona fide GroEL cochaperonins, even capable of substituting for GroES in E. coli growth. A major functional distinction is that only Gp31 and CocO can assi st GroEL in the correct folding of Gp23, the major bacteriophage capsid pro tein. Conserved structural features between CocO and Gp31, which are absent from GroES, highlight their potential importance in specific cochaperonin function.