Rhizobium meliloti and Rhizobium leguminosarum dctD gene products bind to tandem sites in an activation sequence located upstream of sigma 54-dependent dctA promoters.
Free-living rhizobia transport external C4-dicarboxylates to use as sole carbon sources, and uptake of these compounds is essential for nitrogen fixation by rhizobial bacteroids. In both Rhizobium leguminosarum and Rhizobium meliloti, the genes dctB and dctD are believed to form an ntrB/ntrC-like two-component system which regulates the synthesis of a C4-dicarboxylate transport protein encoded by dctA. Here we confirm the identity of sigma 54-dependent promoters previously hypothesized for the R. leguminosarum and R. meliloti dctA genes and demonstrate that repeated, partial dyad symmetry elements located about 75 base pairs upstream of each promoter are essential for fully regulated transcription. Furthermore, we show that both repeats bound dctD protein and that together they resulted in succinate-sensitive transcription when placed upstream of another sigma 54 consensus promoter, that of R. meliloti nifH.
Department of Molecular and Cell Biology, Pennsylvania State University, University Park 16802.
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D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D029382:Dicarboxylic Acid Transporters; D003998:Dicarboxylic Acids / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation / Q000235:genetics*; D015345:Oligonucleotide Probes; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012231:Rhizobium / Q000235:genetics* / Q000378:metabolism; D012808:Sigma Factor / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
D002352:Carrier Proteins; D029382:Dicarboxylic Acid Transporters; D003998:Dicarboxylic Acids; D015345:Oligonucleotide Probes; D012808:Sigma Factor; D014157:Transcription Factors