title: A PhoP-regulated outer membrane protease of Salmonella enterica serovar typhimurium promotes resistance to alpha-helical antimicrobial peptides.
abstract: The outer membrane protein contents of Salmonella enterica serovar Typhimurium strains with PhoP/PhoQ regulon mutations were compared by two-dimensional gel electrophoresis. At least 26 species of outer membrane proteins (OMPs) were identified as being regulated by PhoP/PhoQ activation. One PhoP/PhoQ-activated OMP was identified by semiautomated tandem mass spectrometry coupled with electronic database searching as PgtE, a member of the Escherichia coli OmpT and Yersinia pestis Pla family of outer membrane proteases. Salmonella PgtE expression promoted resistance to alpha-helical cationic antimicrobial peptides (alpha-CAMPs). Strains expressing PgtE cleaved C18G, an 18-residue alpha-CAMP present in culture medium, indicating that protease activity is likely to be the mechanism of OmpT-mediated resistance to alpha-CAMPs. PhoP/PhoQ did not regulate the transcription or export of PgtE, indicating that another PhoP/PhoQ-dependent mechanism is required for PgtE outer membrane localization. PgtE is a posttranscriptionally regulated component of the PhoP/PhoQ regulon that contributes to Salmonella resistance to innate immunity.
authors.affiliation: Departments of Microbiology, University of Washington, Seattle 98195, USA.
authors.forename: T
authors.initials: T
authors.lastname: Guina
authors.forename: E C
authors.initials: EC
authors.lastname: Yi
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Hackett
authors.forename: S I
authors.initials: SI
authors.lastname: Miller
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D004352:Drug Resistance, Microbial; D010450:Endopeptidases / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D013058:Mass Spectrometry; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D010455:Peptides / Q000494:pharmacology*; D017433:Protein Structure, Secondary; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D017422:Sequence Analysis, DNA; D020539:Sequence Analysis, Protein
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D010446:Peptide Fragments; D010455:Peptides; C061064:PhoP protein, Bacteria; D010450:Endopeptidases; C411337:PgtE protein, Salmonella enterica