1887

Abstract

PtxR enhances the expression of the exotoxin A gene . The expression of itself, which occurs from two promoters (P1 and P2), is not completely understood. We have recently demonstrated that the upstream region contains potential binding sites for multiple regulators, including the virulence factor regulator Vfr. In this study, we identified within the upstream region, a 25 bp sequence to which Vfr specifically binds. The sequence is located 20–44 (32.5) bp 5′ of the P2 promoter, and overlaps a potential binding site for the iron-starvation sigma factor PvdS. We also show that, throughout the growth cycle, deletion of reduces expression from the P2 promoter in the strain PAO1 by four- to eightfold, but does not affect expression from P1. Further, loss of Vfr eliminates the PtxR-induced enhancement in the synthesis of exotoxin A and the metalloproteinase LasB. Our results suggest that Vfr modulates and expression in PAO1 through PtxR. A model defining the relationships between these different genes is presented.

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2008-02-01
2020-11-25
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