title: The two-component system PhoPR of Clostridium acetobutylicum is involved in phosphate-dependent gene regulation.
abstract: The phoPR gene locus of Clostridium acetobutylicum ATCC 824 comprises two genes, phoP and phoR. Deduced proteins are predicted to represent a response regulator and sensor kinase of a phosphate-dependent two-component regulatory system. We analyzed the expression patterns of phoPR in P(i)-limited chemostat cultures and in response to P(i) pulses. A basic transcription level under high-phosphate conditions was shown, and a significant increase in mRNA transcript levels was found when external P(i) concentrations dropped below 0.3 mM. In two-dimensional gel electrophoresis experiments, a 2.5-fold increase in PhoP was observed under P(i)-limiting growth conditions compared to growth with an excess of P(i). At least three different transcription start points for phoP were determined by primer extension analyses. Proteins PhoP and an N-terminally truncated *PhoR were individually expressed heterologously in Escherichia coli and purified. Autophosphorylation of *PhoR and phosphorylation of PhoP were shown in vitro. Electromobility shift assays proved that there was a specific binding of PhoP to the promoter region of the phosphate-regulated pst operon of C. acetobutylicum.
authors.affiliation: University of Rostock, Institute of Biological Sciences, Division of Microbiology, Albert-Einstein-Strasse 3, D-18051 Rostock, Germany.
authors.forename: Tomas
authors.initials: T
authors.lastname: Fiedler
authors.forename: Maren
authors.initials: M
authors.lastname: Mix
authors.forename: Uta
authors.initials: U
authors.lastname: Meyer
authors.forename: Stefan
authors.initials: S
authors.lastname: Mikkat
authors.forename: Michael O
authors.initials: MO
authors.lastname: Glocker
authors.forename: Hubert
authors.initials: H
authors.lastname: Bahl
authors.forename: Ralf-Jörg
authors.initials: RJ
authors.lastname: Fischer
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D001483:Base Sequence; D046969:Clostridium acetobutylicum / Q000502:physiology*; D004269:DNA, Bacterial / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D024202:Electrophoretic Mobility Shift Assay; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D008969:Molecular Sequence Data; D010710:Phosphates / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016415:Sequence Alignment; D015398:Signal Transduction; D024363:Transcription Initiation Site
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D010710:Phosphates; C061279:PhoR protein, Bacteria; C061064:PhoP protein, Bacteria