A new major outer membrane protein in derivatives of Escherichia coli carrying the virulence plasmid ColV-K94.

Strains of Escherichia coli K12 harbouring ColV-K94 contain a new major outer membrane protein of molecular weight ca. 33,000. The new protein resembles the Omp A protein in that (1) it is trypsin-sensitive in membrane preparations and (2) it is not murein-associated. The new protein cannot, however, replace the Omp A protein as a functional receptor for the phages K3 and TuII*, for colicin L or for efficient conjugation with F-like donors. The new protein is apparently not a transfer component and is produced by cells unable to produce colicin. Labelling experiments with minicells suggest that the new protein is one of two major plasmid-encoded membrane proteins.