title: A top-down/bottom-up study of the ribosomal proteins of Caulobacter crescentus.
abstract: Ribosomes from the Gram-negative alpha-proteobacterium Caulobacter crescentus were isolated using standard methods. Proteins were separated using a two-dimensional liquid chromatographic system that allowed the analysis of whole proteins by direct coupling to an ESI-QTOF mass spectrometer and of proteolytic digests by a number of mass spectrometric methods. The masses of 53 of 54 ribosomal proteins were directly measured. Protein identifications and proposed post-translational modifications were supported by proteolysis with trypsin, endoprotease Glu-C, and exoproteases carboxypeptidases Y and P. Tryptic peptide mass maps show an average sequence coverage of 62%, and carboxypeptidase C-terminal sequence tagging provided unambiguous identification of the small, highly basic proteins of the large subunit. C. crescentus presents some post-translational modifications that are similar to those of Escherichia coli (e.g., N-terminal acetylation of S9 and S18) along with some unique variations, such as a near absence of L7 and extensive modification of L11. The comprehensive description of this organism's ribosomal proteome provides a foundation for the study of ribosome structure, dependence of post-translational modifications on growth conditions, and the evolution of subcellular organelles.
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Running
authors.forename: Shobha
authors.initials: S
authors.lastname: Ravipaty
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Karty
authors.forename: James P
authors.initials: JP
authors.lastname: Reilly
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D016935:Caulobacter crescentus / Q000378:metabolism*; D002845:Chromatography / Q000379:methods; D002853:Chromatography, Liquid; D004926:Escherichia coli / Q000378:metabolism; D013058:Mass Spectrometry / Q000379:methods; D010455:Peptides / Q000737:chemistry; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D040901:Proteomics / Q000379:methods; D012269:Ribosomal Proteins / Q000737:chemistry*; D012697:Serine Endopeptidases / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D014357:Trypsin / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D010455:Peptides; D012269:Ribosomal Proteins; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase; D014357:Trypsin