title: Quantitative Proteomics of the Infectious and Replicative Forms of Chlamydia trachomatis.
abstract: The obligate intracellular developmental cycle of Chlamydia trachomatis presents significant challenges in defining its proteome. In this study we have applied quantitative proteomics to both the intracellular reticulate body (RB) and the extracellular elementary body (EB) from C. trachomatis. We used C. trachomatis L2 as a model chlamydial isolate for our study since it has a high infectivity:particle ratio and there is an excellent quality genome sequence. EBs and RBs (>99% pure) were quantified by chromosomal and plasmid copy number using PCR, from which the concentrations of chlamydial proteins per bacterial cell/genome were determined. RBs harvested at 15h post infection (PI) were purified by three successive rounds of gradient centrifugation. This is the earliest possible time to obtain purified RBs, free from host cell components in quantity, within the constraints of the technology. EBs were purified at 48h PI. We then used two-dimensional reverse phase UPLC to fractionate RB or EB peptides before mass spectroscopic analysis, providing absolute amount estimates of chlamydial proteins. The ability to express the data as molecules per cell gave ranking in both abundance and energy requirements for synthesis, allowing meaningful identification of rate-limiting components. The study assigned 562 proteins with high confidence and provided absolute estimates of protein concentration for 489 proteins. Interestingly, the data showed an increase in TTS capacity at 15h PI. Most of the enzymes involved in peptidoglycan biosynthesis were detected along with high levels of muramidase (in EBs) suggesting breakdown of peptidoglycan occurs in the non-dividing form of the microorganism. All the genome-encoded enzymes for glycolysis, pentose phosphate pathway and tricarboxylic acid cycle were identified and quantified; these data supported the observation that the EB is metabolically active. The availability of detailed, accurate quantitative proteomic data will be invaluable for investigations into gene regulation and function.
authors.affiliation: Centre for Proteomic Research, Centre for Biological Sciences, University of Southampton, Southampton, United Kingdom.
authors.forename: Paul J S
authors.initials: PJ
authors.lastname: Skipp
authors.affiliation: Waters Corporation, Stamford Avenue, Wilmslow, United Kingdom.
authors.forename: Chris
authors.initials: C
authors.lastname: Hughes
authors.affiliation: Waters Corporation, Stamford Avenue, Wilmslow, United Kingdom.
authors.forename: Thérèse
authors.initials: T
authors.lastname: McKenna
authors.affiliation: School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Australia, and School of Biological Sciences, University of Southampton, Southampton, United Kingdom.
authors.forename: Richard
authors.initials: R
authors.lastname: Edwards
authors.affiliation: Waters Corporation, Stamford Avenue, Wilmslow, United Kingdom.
authors.forename: James
authors.initials: J
authors.lastname: Langridge
authors.affiliation: Pathogen Genomics, The Wellcome Trust Sanger Institute, Hinxton, United Kingdom.
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Thomson
authors.affiliation: Molecular Microbiology Group, School of Medicine, University of Southampton, Southampton, United Kingdom.
authors.forename: Ian N
authors.initials: IN
authors.lastname: Clarke
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002692:Chlamydia trachomatis / Q000502:physiology*; D002522:Chlorocebus aethiops; D004734:Energy Metabolism; D016680:Genome, Bacterial; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics
chemical_list: D001426:Bacterial Proteins; D020543:Proteome