Pseudomonas aeruginosa lasA gene: determination of the transcription start point and analysis of the promoter/regulatory region.

The elastolytic activity of the opportunistic pathogen Pseudomonas aeruginosa is due to the combined activities of at least three secreted proteins: elastase, LasA and alkaline protease. Transcription of both the lasA gene and the elastase structural gene, lasB, requires the transcriptional activator LasR. In order to localize the promoter elements involved in lasA expression, the transcription start point (tsp) for lasA was localized by S1 protection and primer extension analysis. The DNA sequence of the region upstream from the tsp was determined, and a putative sigma promoter was identified. Sequence comparison with the lasB promoter region revealed two areas of considerable homology which could act as potential binding sites for LasR or other, as yet unidentified, regulatory proteins.