Chaperonin-Mediated Folding of Bacteriophage T4 Major Capsid Protein. II. Production of Gene Product 23 Deletion Mutants

Folding of bacteriophage T4 major capsid protein, gene product 23 (534 a.a.), is aided by two proteins: E. coli GroEL chaperonin and viral gp31 co-chaperonin. In the present work a set of mutants with extensive deletions inside gene 23 using controlled digestion with Bal31 nuclease has been constructed. Proteins with deletions were co-expressed from plasmid vectors with phage gp31 co-chaperonin. Deletions from 8 to 33 a.a. in the N-terminal region of the gp23 molecule covering the protein proteolytic cleavage site during capsid maturation have no influence on the mutants' ability to produce in E. coli cells proteins which form regular structures—polyheads. Deletions in other regions of the polypeptide chain (187-203 and 367-476 a.a.) disturb the correct folding and subsequent assembly of gp23 into polyheads.