The gene H spike protein of bacteriophages ∅X174 and S13: I. Functions in phage-receptor recognition and in transfection

Abstract

The gene H protein of bacteriophage ∅X174 is a coat component located in the spikes at the vertices of the polyhedron. In extracts of ∅X174-infected cells, the gene H protein binds to exogenous single-stranded phage DNA enhancing its infectivity in transfection of spheroplasts. This stimulation was not observed with extracts deficient in gene H protein. Transfection by the gene H protein-DNA complex was specifically inhibited by antibody to gene H protein. Lipopolysaccharide derived from ∅X174-sensitive cells blocked transfection by the DNA complex with gene H protein but not by the DNA alone, suggesting that the gene H protein functions as the phage adsorption protein by recognizing the phage lipopolysaccharide receptor. Gene H protein from ∅X174 stimulated the transfection by single-stranded DNA from the closely related phage S13; this stimulation was blocked by antibody to gene H protein and by the ∅X174 lipopolysaccharide receptor. These actions in phage-receptor recognition and in transfection suggest that the gene H protein has multiple functions and behaves as a “pilot protein” in guiding the phage and its DNA through several stages of the infection cycle.