MOLECULAR CHARACTERIZATION AND REGULATION OF AN OPERON ENCODING A SYSTEM FOR TRANSPORT OF ARGININE AND ORNITHINE AND THE ARGR REGULATORY PROTEIN IN PSEUDOMONAS-AERUGINOSA

The complete nucleotide sequence for the aot operon of Pseudomonas aer uginosa PAO1 was determined. This operon contains six open reading fra mes, The derived sequences for four of these, aotJ, aotQ, aotM, and ao tP, show high similarity to those of components of the periplasmic bin ding protein-dependent ABC (ATP binding cassette) transporters of ente ric bacteria. Transport studies with deletion derivatives established that these four genes function in arginine-inducible uptake of arginin e and ornithine but not lysine, The aotO gene, which encodes a polypep tide with no significant similarity to any known proteins, is not esse ntial for arginine and ornithine uptake. The sixth and terminal gene i n the operon encodes ArgR, which has been recently shown to function i n regulation of arginine metabolism. Studies with an aotJ::lacZ transl ational fusion showed;that expression of the aot operon is strongly in duced by arginine and that this effect is mediated by ArgR, S1 nucleas e and primer extension experiments showed the presence of two promoter s, P1 and P2, The downstream promoter, P2, is induced by arginine and appears to be subject to carbon catabolite repression. The upstream pr omoter, P1, is induced by glutamate, Footprinting experiments establis hed the presence of a 44-bp ArgR binding site that overlaps the -35 re gion for P2, as was shown to be the case for the arginine-inducible ar u promoter, and the -10 region for P1, as was shown to be the case for arginine-repressible operons in P. aeruginosa, Sequence alignment con firms the architecture and the consensus sequence of the ArgR binding sites, as was previously reported.