tolA, tolB and excC, three cistrons involved in the control of pleiotropic release of periplasmic proteins by Escherichia coli K12.

Mutants of Escherichia coli K12 carrying exc mutations inducing the release of the plasmid pBR322-encoded beta-lactamase (EC 3.5.2.6) into the extracellular medium were analysed and compared with previously described excretory mutants carrying lky mutations associated with the release of alkaline phosphatase and to tolA and tolB mutants, originally described as tolerant towards various colicins. The exc, lky and tol mutations mapped near the gal operon at min 16.5 of the E. coli linkage map. A genetic analysis presented in this paper showed that some exc and lky mutations belonged to the tolA and tolB complementation groups. Furthermore, we identified a third cistron, excC, involved in the excretion of periplasmic enzymes but distinct from the two others.