THE TOLQRA PROTEINS ARE REQUIRED FOR MEMBRANE INSERTION OF THE MAJOR CAPSID PROTEIN OF THE FILAMENTOUS PHAGE F1 DURING INFECTION

Infection of Escherichia coli by the filamentous bacteriophage f1 is i nitiated by interaction of the end of the phage particle containing th e gene III protein with the tip of the F conjugative pilus. This is fo llowed by the translocation of the phage DNA into the cytoplasm and th e insertion of the major phage capsid protein, pVIII, into the cytopla smic membrane. DNA transfer requires the chromosomally encoded TolA, T olQ, and TolR cytoplasmic membrane proteins. By using radiolabeled pha ges, it can be shown that no pVIII is inserted into the cytoplasmic me mbrane when the bacteria contain null mutations in tolQ, -R and -A. Th e rate of infection can be varied by using bacteria expressing various mutant TolA proteins. Analysis of the infection process in these stra ins demonstrates a direct correlation between the rate of infection an d the incorporation of infecting bacteriophage pVIII into the cytoplas mic membrane.