Purification of characterization of gene 8 product of bacteriophage T3.

The product of gene 8 (gp8) of T3 phage was purified from proheads, heads, and extract prepared from cells infected with a mutant defective in gene 10 (major head protein) (10- extract). gp8, when purified by hydrophobic column chromatography from proheads solubilized by guanidine hydrochloride, did not show any ordered structure. gp8 from heads ruptured by sucrose shock sedimented with a sedimentation coefficient of 20 S (20 S assembly). Electron micrography of 20 S assemblies showed ring structures displaying radial symmetry. When the gp8 in 20 S assemblies was concentrated, it formed two-dimensional crystals. gp8 in 20 S material was detected in 10- extract by sedimentation analysis. gp8 purified from 10- extract by anti-gp8 antibody column chromatography had an ordered structure identical to that of the 20 S assembly from heads. The effect of anti-gp8 serum on the activity of proheads and heads was examined by in vitro complementation. Anti-gp8 serum preabsorbed with 5- X 8- -extracted inactivated proheads and heads. Anti-gp8 serum preabsorbed with proheads inactivated heads but not proheads. Similarly, anti-gp8 serum preabsorbed with phage-inactivated proheads but not heads. From these results, it is concluded that gp8 in proheads and heads is accessible to antibodies and that different antigenic sites of gp8 are exposed in proheads and heads.