title: Targeted protein degradation by Salmonella under phagosome-mimicking culture conditions investigated using comparative peptidomics.
abstract: The pathogen Salmonella enterica is known to cause both food poisoning and typhoid fever. Because of the emergence of antibiotic-resistant isolates and the threat of bioterrorism (e.g. contamination of the food supply), there is a growing need to study this bacterium. In this investigation, comparative peptidomics was used to study S. enterica serovar Typhimurium cultured in either a rich medium or in an acidic, low magnesium, and minimal nutrient medium designed to roughly mimic the macrophage phagosomal environment (within which Salmonella are known to survive). Native peptides from cleared cell lysates were enriched by using isopropanol extraction and analyzed by using both LC-MS/MS and LC-FTICR-MS. We identified and quantified 5,163 peptides originating from 682 proteins, and the data clearly indicated that compared with Salmonella cultured in the rich medium, cells cultured in the phagosome-mimicking medium had dramatically higher abundances of a wide variety of protein degradation products, especially from ribosomal proteins. Salmonella from the same cultures were also analyzed using traditional, bottom-up proteomic methods, and when the peptidomics and proteomics data were analyzed together, two clusters of proteins targeted for proteolysis were tentatively identified. Possible roles of targeted proteolysis by phagocytosed Salmonella are discussed.
authors.affiliation: Fundamental Science Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
authors.forename: Nathan P
authors.initials: NP
authors.lastname: Manes
authors.forename: Jean K
authors.initials: JK
authors.lastname: Gustin
authors.forename: Joanne
authors.initials: J
authors.lastname: Rue
authors.forename: Heather M
authors.initials: HM
authors.lastname: Mottaz
authors.forename: Samuel O
authors.initials: SO
authors.lastname: Purvine
authors.forename: Angela D
authors.initials: AD
authors.lastname: Norbeck
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Monroe
authors.forename: Jennifer S D
authors.initials: JS
authors.lastname: Zimmer
authors.forename: Thomas O
authors.initials: TO
authors.lastname: Metz
authors.forename: Joshua N
authors.initials: JN
authors.lastname: Adkins
authors.forename: Richard D
authors.initials: RD
authors.lastname: Smith
authors.forename: Fred
authors.initials: F
authors.lastname: Heffron
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D002853:Chromatography, Liquid; D003470:Culture Media; D006801:Humans; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D010588:Phagosomes / Q000378:metabolism; D040901:Proteomics / Q000379:methods*; D012486:Salmonella typhimurium / Q000378:metabolism* / Q000472:pathogenicity; D053719:Tandem Mass Spectrometry
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D010446:Peptide Fragments