The gene H spike protein of bacteriophages ∅X174 and S13: II. Relation to synthesis of the parental replicative form

Abstract

Several molecules of the ∅X174 gene H protein, a component of the phage spike, become firmly associated with the host cell upon infection and resist protease treatment of the cell. The gene H protein was recovered in association with the phage DNA converted to the duplex replicative form and was bound to several different regions of the DNA. Similar results were obtained with the gene H protein of the related phage S13. Cells infected with a temperature-sensitive mutant of S13 in gene H failed to make parental replicative form at the restrictive temperature, although phage binding and eclipse occurred at normal levels. Since phage penetration is coupled to replication and the gene H protein is recovered tightly bound to the parental replicative form, this protein is presumed to participate in the first stage of DNA synthesis. These and related findings form the basis for a general proposal of a “pilot protein” as a minor component of the virus with multiple functions in adsorption, penetration, and early intracellular stages of viral chromosome expression.