A Second Operator Is Involved in Pseudomonas aeruginosa Elastase ( lasB ) Activation

Abstract

ABSTRACT Pseudomonas aeruginosa LasB elastase gene ( lasB ) transcription is controlled by the two-component quorum-sensing system of LasR, and the autoinducer, 3OC 12 -HSL ( N -3-[oxododecanoyl]homoserine lactone). LasR and 3OC 12 -HSL-mediated lasB activation requires a functional operator sequence (OP1) in the lasB promoter region. Optimal activation of lasB , however, requires a second sequence of 70% identity to OP1, named OP2, located 43 bp upstream of OP1. In this study, we used sequence substitutions and insertion mutations in lasB p- lacZ fusion plasmids to explore the role of OP2 in lasB activation. Our results demonstrate that (i) OP1 and OP2 synergistically mediate lasB activation; (ii) OP2, like OP1, responds to LasR and 3OC 12 -HSL; and (iii) the putative autoinducer-binding domain of LasR is not required for synergistic activation from OP1 and OP2.