Isolation and reassembly of bacteriophage T4 core proteins.

The products of genes 22, 67 and 68, and the internal proteins IPI, IPII and IPIII, as components of the scaffolding core of the bacteriophage T4 prohead, have been isolated and purified by hydroxylapatite column chromatography. Under conditions promoting reassembly in vitro, the proteins associated into elongated particles of practically constant width but variable length that we have called polycores. Preliminary optical diffraction experiments indicate that polycores may have an ordered structure, possibly helical, as has been suggested for the polyhead core. The coassembly of core proteins and the purified shell protein gp23 results in the formation of core-containing polyheads. Occasionally, prolate core-like particles have been observed but their reproducible formation has not been attained. Attempts to investigate the role of the minor prohead component gp20 in core assembly have been made through the cloning of the corresponding gene in an expression vector and subsequent purification of the protein.