Functions of gene C and gene D products of bacteriophage phi X 174

Abstract

Phage-related materials existing in cells infected with various mutants of bacteriophage phi chi 174 were investigated. A novel species of replicative-form (RF) DNA was found in cells infected with a phage mutant of gene B, C, D, F, or G. This species, called RFI, sedimented at a position between RFI and RFII in a neutral sucrose gradient. It was converted to RFI upon denaturation in alkali, denaturation in formamide and subsequent renaturation, or RNase treatment at low ionic strength. In cells infected with a phage mutant of gene C, RFI was derived from pulse-labeled RFII after a short chase. TLLS INFECTED WITH A MUTANT OF GENE B, D, or F. A possible function of the C gene product of phi chi 174 could be to prevent the conversion of RFII to RFI, thereby maintaining the availability of RFII to act as the template for single-stranded viral DNA synthesis. A protein complex containing no DNA, which sedimented with an S value of 108 in a sucrose gradient and contained virion proteins F, G, and H, and nonvirion protein D, was found in cells infected with the gene C mutant. A possible function of protein D was considered as a scaffolding protein for assembly of phage structural proteins.