ASSEMBLY OF A FUNCTIONAL PHAGE PRD1 RECEPTOR DEPENDS ON 11 GENES OF THE INCP PLASMID MATING PAIR FORMATION COMPLEX

PRD1, a lipid-containing double-stranded DNA bacteriophage, uses the m ating pair formation (Mpf) complex encoded by conjugative IncP plasmid s as a receptor. Functions responsible for conjugative transfer of Inc P plasmids are encoded by two distinct regions, Tra1 and Tra2. Ten Tra 2 region gene products (TrbB to TrbL) and one from the Tra1 region (Tr aF) form the Mpf complex. We carried out a mutational analysis of the PRD1 receptor complex proteins by isolating spontaneous PRD1-resistant mutants. The mutations were distributed among the trb genes in the Tr a2 region and accumulated predominately in three genes, trbC, trbE, an d trbL. Three of 307 phage-resistant mutants were weakly transfer prof icient. Mutations causing a phage adsorption-deficient, transfer-posit ive phenotype were analyzed by sequencing.