title: Identification of a TRAP transporter for malonate transport and its expression regulated by GtrA from Sinorhizobium meliloti.
abstract: Sinorhizobium meliloti can live as a saprophyte in soil or as a nitrogen-fixing symbiont inside the root nodule cells of alfalfa and related legumes by utilizing different organic compounds as its carbon source. Here we have identified the matPQMAB operon in S. meliloti 1021. Within this operon, matP, matQ and the M region of the fused gene matMA encode an extracytoplasmic solute receptor, a small transmembrane protein and a large transmembrane protein, consisting of three components of the tripartite ATP-independent periplasmic (TRAP) transporter for malonate transport. The A region of the fused gene matMA and matB encode malonate-metabolizing enzymes, malonyl-CoA decarboxylase and malonyl-CoA synthetase. The null mutant of each matPQMAB gene is unable to grow on M9 minimal medium containing malonate as the sole carbon source. However, these mutants can induce the formation of efficient nitrogen-fixing root nodules on alfalfa. The matPQMAB operon is expressed in free-living bacterial cells and symbiotic bacterial cells from infection threads and root nodules. The GntR family transcriptional regulator, GtrA, specifically binds the promoter of the matPQMAB operon, positively regulating its expression. Moreover, the matPQMAB can be transcriptionally induced by malonate. These results suggested that a C(3)-dicarboxylic acid TRAP transporter is responsible for malonate transport in S. meliloti.
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Ai-Min
authors.initials: AM
authors.lastname: Chen
authors.forename: Yong-Bao
authors.initials: YB
authors.lastname: Wang
authors.forename: Sun
authors.initials: S
authors.lastname: Jie
authors.forename: Ai-Yuan
authors.initials: AY
authors.lastname: Yu
authors.forename: Li
authors.initials: L
authors.lastname: Luo
authors.forename: Guan-Qiao
authors.initials: GQ
authors.lastname: Yu
authors.forename: Jia-Bi
authors.initials: JB
authors.lastname: Zhu
authors.forename: Yan-Zhang
authors.initials: YZ
authors.lastname: Wang
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism; D029382:Dicarboxylic Acid Transporters / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D017136:Ion Transport; D008314:Malonates / Q000378:metabolism*; D000455:Medicago sativa / Q000382:microbiology; D009586:Nitrogen Fixation / Q000235:genetics; D009876:Operon; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012329:RNA, Bacterial; D016962:Sinorhizobium meliloti / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D013559:Symbiosis / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D029382:Dicarboxylic Acid Transporters; D008314:Malonates; D012329:RNA, Bacterial; D014157:Transcription Factors; C030290:malonic acid; D000445:Aldehyde Oxidoreductases; C067282:glutamyl tRNA reductase; D002262:Carboxy-Lyases; C021532:malonyl-CoA decarboxylase; D003066:Coenzyme A Ligases; C021533:malonyl-CoA synthetase