Characterization of an Endoprotease (PrpL) Encoded by a PvdS-Regulated Gene inPseudomonas aeruginosa

Open Access
Publisher Website
Google Scholar
Abstract
The expression of many virulence factors inPseudomonas aeruginosais dependent upon environmental conditions, including iron levels, oxygen, temperature, and osmolarity. The virulence ofP. aeruginosaPAO1 is influenced by the iron- and oxygen-regulated gene encoding the alternative sigma factor PvdS, which is regulated through the ferric uptake regulator (Fur). We observed that overexpression of PvdS in strain PAO1 and a ΔpvdS::Gmmutant resulted in increased pyoverdine production and proteolytic activity compared to when PvdS was not overexpressed. To identify additional PvdS-regulated genes, we compared extracellular protein profiles from PAO1 and the ΔpvdS::Gmmutant grown under iron-deficient conditions. A protein present in culture supernatants from PAO1 but not in supernatants from ΔpvdS::Gmwas investigated. Amino acid sequence analysis and examination of the genomic database of PAO1 revealed that the N terminus of this 27-kDa protein is identical to that of protease IV ofP. aeruginosastrain PA103-29 and is homologous to an endoprotease produced byLysobacter enzymogenes.In this study, the gene encoding an endoprotease was cloned from PAO1 and designatedprpL(PvdS-regulated endoprotease, lysyl class). All (n= 41) but one of the strains ofP. aeruginosa, including clinical and environmental isolates, examined carryprpL. Moreover, PrpL production among these strains was highly variable. Analysis of RNase protection assays identified the transcription initiation site ofprpLand confirmed that its transcription is iron dependent. In the ΔpvdS::Gmmutant, the level ofprpLtranscription was iron independent and decreased relative to the level in PAO1. Furthermore, transcription ofprpLwas independent of PtxR, a PvdS-regulated protein. Finally, PrpL cleaves casein, lactoferrin, transferrin, elastin, and decorin and contributes to PAO1's ability to persist in a rat chronic pulmonary infection model.

This publication has 81 references indexed in Scilit: