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The Bacillus subtilis phage varphi29-encoded membrane protein p16.7 is one of the few proteins known to be involved in prokaryotic membrane-associated DNA replication. Protein p16.7 contains an N-terminal transmembrane domain responsible for membrane localization. A soluble variant lacking the N-terminal membrane anchor, p16.7A, forms dimers in solution, binds to DNA, and has affinity for the varphi29 terminal protein. Here we show that the soluble N-terminal half of p16.7A can form a dimeric coiled coil. However, a second domain, located in the C-terminal half of the protein, has been characterized as being the main domain responsible for p16.7 dimerization. This 70-residue C-terminal domain, named p16.7C, also constitutes the functional part of the protein as it binds to DNA and terminal protein. Sequence alignments, secondary structure predictions, and spectroscopic analyses suggest that p16.7C is evolutionarily related to DNA binding homeodomains, present in many eukaryotic transcriptional regulator proteins. Based on the results, a structural model of p16.7 is presented.


Daniel Muñoz-Espín, Mauricio G Mateu, Laurentino Villar, Anabel Marina, Margarita Salas, Wilfried J J Meijer. Phage phi29 DNA replication organizer membrane protein p16.7 contains a coiled coil and a dimeric, homeodomain-related, functional domain. The Journal of biological chemistry. 2004 Nov 26;279(48):50437-45

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PMID: 15371435

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