A new colicin that adsorbs to outer-membrane protein Tsx but is dependent on the tonB instead of the tolQ membrane transport system.

A new colicin, Col5, was synthesized by an Escherichia coli isolate of human origin from the ECOR Collection. It was unique because it adsorbed to the outer-membrane protein Tsx, but used the tonB rather than the tolQ membrane transport system, which is employed by the only other Tsx-specific colicin, ColK. Col5 was encoded by a 5.2 kb plasmid, p5. It was inducible by mitomycin C, and strains harbouring p5 exhibited quasi-lysis. The bactericidal protein had an M(r) of 56,000.