Heterogeneity of the procapsid of bacteriophage T3

Like other double-stranded DNA bacteriophages, bacteriophage T3 assembles a DNA-free procapsid that subsequently packages the bacteriophage DNA. By agarose gel electrophoresis, it has been found that the T3 procapsid has a negative electrophoretic mobility (μ) that progressively increases in magnitude by as much as 3% after assembly of the procapsid. This increase is (1) caused by an increase in the solid support-free μ (μ(o)) of the procapsid, not a decrease in its radius, and (2) not prevented by either genetically or chemically (use of proflavine) blocking DNA packaging. However, inhibition of the formation of high-energy compounds with a mixture of cyanide and fluoride ions does block the time-dependent increase in the magnitude of μ(o). This increase appears to be accompanied by addition of an undentified T3 protein to the procapsid.