THE VFR GENE-PRODUCT, REQUIRED FOR PSEUDOMONAS-AERUGINOSA EXOTOXIN-A AND PROTEASE PRODUCTION, BELONGS TO THE CYCLIC-AMP RECEPTOR PROTEIN FAMILY

The synthesis of exotoxin A (ETA) by Pseudomonas aeruginosa is a compl ex, regulated event. Several ETA putative regulatory mutants of P. aer uginosa PA103 have previously been characterized (S. E. H. West, S. A. Kaye, A. N. Hamood, and B. H. Iglewski, Infect. Immun. 62:897-903, 19 94). In addition to ETA production, these mutants, PA103-15, PA103-16, and PA103-19, were also deficient in the production of protease and i n regA P1 promoter activity. RegA is a positive regulator of ETA trans cription. We cloned a gene, designated vfr for virulence factor regula tor, that restored ETA and protease production to parental levels in t hese mutants. In addition, transcription from the regA P1 promoter was restored. In Escherichia coli, when vfr was overexpressed from a phag e T7 promoter, a protein with an apparent molecular mass of 28.5 kDa w as produced. Analysis of the deduced amino acid sequence of vfr reveal ed that the expected protein is 67% identical and 91% similar over a 2 02-amino-acid overlap to the E. coli cyclic AMP receptor protein (CAP or Crp). The cloned vfr gene complemented the beta-galactosidase- and tryptophanase deficient phenotypes of E. coil RZ1331, a crp deletion m utant. However, the E. coli crp gene under the control of the tac prom oter did not complement the ETA-deficient or protease-deficient phenot ype of PA103-15 or PA103-16. The ability of vfr to restore both ETA an d protease production to these mutants suggests that vfr is a global r egulator of virulence factor expression in P. aeruginosa.