title: Probing for pH-regulated proteins in Sinorhizobium medicae using proteomic analysis.
abstract: To elucidate the mechanisms of pH response in an acid-tolerant Sinorhizobium medicae strain we have identified acid-activated gene transcription and now complement this approach by using a proteomic analysis to identify the changes that occur following exposure to acidity. Protein profiles of persistently or transiently acid-stressed S. medicae cells were compared to those grown in pH neutral, buffered media. Fifty pH-regulated proteins were identified; N-terminal sequences for 15 of these were obtained using the Edman degradation. Transient acid exposure downregulated GlnA and GlnK and upregulated a hypothetical protein. Continuing acid exposure downregulated ClpP, an ABC transporter, a hypothetical protein, a lipoprotein, the Trp-like repressor WrbA1 and upregulated DegP, fructose bisphosphate aldolase, GroES, malate dehydrogenase and two hypothetical proteins. These findings implicate proteolytic, chaperone and transport processes as key components of pH response in S. medicae.
authors.affiliation: Centre for Rhizobium Studies, School of Biological Sciences and Biotechnology, Murdoch University, Murdoch, Australia. reeve@murdoch.edu.au
authors.forename: Wayne G
authors.initials: WG
authors.lastname: Reeve
authors.forename: Ravi P
authors.initials: RP
authors.lastname: Tiwari
authors.forename: Nelson
authors.initials: N
authors.lastname: Guerreiro
authors.forename: Janine
authors.initials: J
authors.lastname: Stubbs
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dilworth
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Glenn
authors.forename: Barry G
authors.initials: BG
authors.lastname: Rolfe
authors.forename: Michael A
authors.initials: MA
authors.lastname: Djordjevic
authors.forename: John G
authors.initials: JG
authors.lastname: Howieson
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D020543:Proteome; D020579:Sinorhizobium / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D010446:Peptide Fragments; D020543:Proteome