Enterobacteria phage M13 — Gene VII (G7P / pVII)

Overview

• UniProt Accession: P69535 (G7P_BPM13)
• Gene Symbol: VII
• Protein Product: Tail (distal tip) minor coat protein G7P (pVII, Coat protein C polypeptide I), 33 aa (~3.6 kDa) single-pass hydrophobic peptide (file:BPM13/VII/VII-uniprot.txt).

Biological Role in the M13 Lifecycle

• Distal ("Round") Virion Tip Plug: In the mature M13 filamentous virion (cryo-EM structure at 3.50 Å, PDB: 8IXL, 8JWW), five copies of pVII form a C5-symmetric α-helical plug at the apex of the distal ("tail" / round) tip, surrounded by a pentameric ring of pIX and the first layer of major coat protein pVIII (file:BPM13/VII/VII-uniprot.txt).
• Initiation of Virion Assembly and Extrusion: Prior to assembly, pVII inserts spontaneously (Sec/YidC-independently) into the Escherichia coli inner membrane (GO:0020002 host cell plasma membrane) PMID:35746635. Together with pIX, pVII enters the inner-membrane pI/pXI assembly complex laterally and recognizes the exposed hairpin packaging signal of the progeny (+)ssDNA via its positively charged C-terminus, forming the distal cap that emerges first from the host cell to initiate concomitant virion assembly and extrusion (GO:0099045 viral extrusion, GO:0019068 virion assembly) (file:BPM13/VII/VII-uniprot.txt, PMID:35746635).

Key GO Annotations

• Molecular Function: GO:0039660 (structural constituent of virion).
• Cellular Component: GO:0019028 (viral capsid) and GO:0020002 (host cell plasma membrane).
• Biological Process: GO:0099045 (viral extrusion) and GO:0019068 (virion assembly).