Putative Head-Tail Connector Protein Yqbg from Bacillus subtilis and similar proteins
The uncharacterized Bacillus subtilis Yqbg protein, whose gene is part of the unusual genetic element called skin, shows a similar structure to the connector proteins gp6 and gp15 from bacteriophage HK97 and SPP1, respectively. gp6 and gp15 are critical in the assembly of the connector, a specialized structure that serves as an interface for head and tail attachment, as well as a point at which DNA exits the head during infection by the bacteriophage. They form dodecameric ring structures that comprise the middle ring of the connector, located between the portal protein (attached to the head) and the gp7/gp16 ring (attached to the tail). The Yqbg gene is surrounded with genes similar to genes in the Bacillus subtilis prophage-like element PBSX, which encode for proteins comprising contractile-tailed phage-like particles that are produced upon mitomycin C treatment. Yqbg likely acts as a head-tail connector protein, similar to gp6 and gp15, of the PBSX-like prophage encoded in the skin element.