Co-expression of gene 31 and 23 products of bacteriophage T4

Folding of the major capsid protein of bacteriophage T4 encoded by gene 23 is aided by Escherichia coli GroEL chaperonin and phage co-chaperonin gp31. In the absence of gene product (gp) 31, aggregates of recombinant gp23 acc umulate in the cell similar to inclusion bodies. These aggregates can be so lubilized with 6 M urea. However, the protein cannot form regular structure s in solution. A system of co-expression of gp31 and gp23 under the control of phage T7 promoter in E. coil cells has been constructed. Folding of ent ire-length gp23 (534 amino acid residues) in this system results in the cor rectly folded recombinant gp23, which forms long regular structures (polyhe ads) in the cell.