The Bacillus subtilis Phage φ29 Protein p16.7, Involved in φ29 DNA Replication, Is a Membrane-localized Single-stranded DNA-binding Protein

Abstract

The functional role of the φ29-encoded integral membrane protein p16.7 in phage DNA replication was studied using a soluble variant, p16.7A, lacking the N-terminal membrane-spanning domain. Because of the protein-primed mechanism of DNA replication, the bacteriophage φ29 replication intermediates contain long stretches of single-stranded DNA (ssDNA). Protein p16.7A was found to be an ssDNA-binding protein. In addition, by direct and functional analysis we show that protein p16.7A binds to the stretches of ssDNA of the φ29 DNA replication intermediates. Properties of protein p16.7A were compared with those of the φ29-encoded single-stranded DNA-binding protein p5. The results obtained show that both proteins have different, non-overlapping functions. The likely role of p16.7 in attaching φ29 DNA replication intermediates to the membrane of the infected cell is discussed. Homologues of gene 16.7 are present in φ29-related phages, suggesting that the proposed role of p16.7 is conserved in this family of phages.