T4 gene 40 mutants: II. Phenotypic properties

Abstract

Evidence is presented that p40 affects the solubility of p20 inside the T4-infected cell. In the absence of p20 and p40 function at high temperature, p20 is located specifically and exclusively in the cell envelope. It is possible that p40 may interact with p20 before head assembly can be initiated. Cleavage of the major head protein in gene 40 mutant-infected cells is also inhibited. In addition to producing single-layered polyheads and phage at 30°, am restrictive cells infected with gene 40 am mutants produce some empty capsids. It is likely that p40 function is only strictly required for phage growth at high temperature. Electron microscopy of thin sections of crude cell envelopes showed few recognizable structural components, although most phage structural proteins were present upon sodium dodecyl sulfate-gel electrophoresis of envelope preparations. Extraction with sodium chloride selectively removes some of the viral proteins from the crude cell envelope preparation, while extraction with 4 M guanidine · HCl greatly reduces the amount of T4 protein in the cell envelopes. The envelope association of most of these proteins appears to be nonspecific.