Positive control of Pseudomonas aeruginosa amidase synthesis is mediated by a transcription anti-termination mechanism.

The DNA sequence of the region upstream from the amidase structural gene (amiE) of Pseudomonas aeruginosa indicates that amidase (EC 3.5.1.4) is transcribed from an Escherichia coli-like promoter located 150 bp before the amiE translation initiation codon. The sequence between the promoter and the coding sequence includes a single open reading frame followed by an E. coli-like rho-independent transcription terminator. A deletion within the presumed terminator region which disrupts the potential stem/loop formation leads to high constitutive amidase expression which is independent of the product of the regulator gene (amiR). It is proposed that the catabolic aliphatic amidase of P. aeruginosa is regulated by a transcription anti-termination mechanism. The magnoconstitutive mutant PAC433 has promoter and terminator sequences identical to the wild-type PAC1 but contains a single base pair change in the amiE gene ribosome-binding site.