XCP-MEDIATED PROTEIN SECRETION IN PSEUDOMONAS-AERUGINOSA - IDENTIFICATION OF 2 ADDITIONAL GENES AND EVIDENCE FOR REGULATION OF XCP GENE-EXPRESSION

In Pseudomonas aeruginosa, several exoproteins synthesized with a sign al sequence (elastase, lipase, phospholipases, alkaline phosphatase an d exotoxin A) are secreted by a two-step mechanism. They first cross t he inner membrane in a signal sequence-dependent way, and are further translocated across the outer membrane in a second step requiring secr etion functions encoded by several xcp genes. Ten xcp genes have alrea dy been characterized (Bally et al., 1992a). In this study, two additi onal xcp genes, xcpP and xcpQ, are described. They are located in the 40 min region of the chromosome where they probably define an operon, divergent from the xcpR-Z operon previously characterized in this regi on. These two genes encode two proteins, XcpP and XcpQ, similar to Pul C and PulD of the pul system of Klebsiella oxytoca. Moreover, the two divergent operons share a common regulation which is growth-phase depe ndent.