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Gene Review

dctA  -  C4-dicarboxylate transporter DctA

Sinorhizobium meliloti 1021

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Disease relevance of dctA

  • Cooperative binding of DctD to the dctA upstream activation sequence of Rhizobium meliloti is enhanced in a constitutively active truncated mutant [1].
  • Sinorhizobium meliloti dctA mutants with partial ability to transport dicarboxylic acids [2].
  • Using the toxicity of the DctA substrate fluoroorotic acid as a selective agent in an iterated selection procedure, four independent S. meliloti dctA mutants were isolated that retained some ability to transport dicarboxylates [2].
  • Isolation and characterization of Azospirillum lipoferum locus that complements Rhizobium meliloti dctA and dctB mutations [3].

High impact information on dctA

  • The dctD gene product (DCTD) activates transcription from dctA by the sigma 54-holoenzyme form of RNA polymerase in Rhizobium meliloti [4].
  • Purified DCTDL143 recognized the DCTD-binding sites at the dctA promoter region and catalyzed the isomerization of closed complexes between sigma 54-holoenzyme and the dctA promoter to open complexes [4].
  • Analysis of the fusions in various mutant backgrounds demonstrated that dctB, dctD, and ntrA products are required for dctA expression [5].
  • DctD(Delta1-142), a truncated and constitutively active form of the sigma(54)-dependent activator DctD from Sinorhizobium meliloti, displayed an altered DNase I footprint at its binding site located upstream of the dctA promoter in the presence of ATP [6].
  • These data suggest that both rhizobial species have an IHF homolog that stimulates DctD-mediated transcriptional activation from the R. leguminosarum dctA promoter [7].

Chemical compound and disease context of dctA


Biological context of dctA

  • Here we characterize an element (UAS) located upstream of dctA that has tandem binding sites for the dctD gene product (DctD) [9].
  • These symbiotic phenotypes are consistent with previous suggestions that dctA expression in bacteroids can occur independently of dctB and dctD [5].
  • Characterization of this fragment by subcloning, transposon mutagenesis, and complementation analysis revealed three loci, designated dctA, dctB, and dctD [5].
  • Mutation of R. meliloti dctD showed that it was not essential for symbiotic nitrogen fixation but was needed for growth on succinate and the expression of a dctA-lacZ fusion gene in free-living cells [10].
  • Complementation of Rhizobium leguminosarum dct mutants with a cosmid bank yielded Rhizobium meliloti homologs of the dctA, dctB, and dctD genes [10].

Anatomical context of dctA

  • The dctA-encoded protein is highly hydrophobic and contains eight potential transmembrane helices, indicating that it is probably the structural component of the transport system responsible for movement of dicarboxylates from the periplasm across the inner membrane [11].

Associations of dctA with chemical compounds

  • They encode proteins with homology to the R. leguminosarum bv. viceae dicarboxylate transport proteins regulating expression of dctA and to other proteins comprising two-component regulatory systems [11].
  • Two others were located on the pRmeSU47b megaplasmid: one was a new locus which was induced by luteolin and encoded a membrane protein, and the other was dctA, the structural gene for dicarboxylic acid transport [12].
  • Mutations in the dctA and dctB genes both resulted in the reduction, but not elimination, of chemotactic responses to succinate, indicating that transport via DctA or chemosensing via DctB is not essential for C4 dicarboxylate taxis, although they appear to contribute to it [13].
  • The transcriptional induction of the dctA gene by environmental signals was decreased by DNA gyrase inhibitors such as novobiocin and coumermycin [14].
  • Construction of an ntrA mutant of A. tumefaciens by site-directed insertional mutagenesis demonstrated the requirement of the ntrA gene for nitrate utilization and C4-dicarboxylate transport but not for vir gene expression or tumorigenesis [15].

Analytical, diagnostic and therapeutic context of dctA


  1. Cooperative binding of DctD to the dctA upstream activation sequence of Rhizobium meliloti is enhanced in a constitutively active truncated mutant. Scholl, D., Nixon, B.T. J. Biol. Chem. (1996) [Pubmed]
  2. Sinorhizobium meliloti dctA mutants with partial ability to transport dicarboxylic acids. Yurgel, S.N., Kahn, M.L. J. Bacteriol. (2005) [Pubmed]
  3. Isolation and characterization of Azospirillum lipoferum locus that complements Rhizobium meliloti dctA and dctB mutations. Tripathi, A.K., Mishra, B.M. Can. J. Microbiol. (1996) [Pubmed]
  4. Constitutive ATP hydrolysis and transcription activation by a stable, truncated form of Rhizobium meliloti DCTD, a sigma 54-dependent transcriptional activator. Lee, J.H., Scholl, D., Nixon, B.T., Hoover, T.R. J. Biol. Chem. (1994) [Pubmed]
  5. Analysis of C4-dicarboxylate transport genes in Rhizobium meliloti. Yarosh, O.K., Charles, T.C., Finan, T.M. Mol. Microbiol. (1989) [Pubmed]
  6. Nucleotide-dependent conformational changes in the sigma54-dependent activator DctD. Wang, Y.K., Park, S., Nixon, B.T., Hoover, T.R. J. Bacteriol. (2003) [Pubmed]
  7. A rhizobial homolog of IHF stimulates transcription of dctA in Rhizobium leguminosarum but not in Sinorhizobium meliloti. Sojda, J., Gu, B., Lee, J., Hoover, T.R., Nixon, B.T. Gene (1999) [Pubmed]
  8. Rhizobium meliloti ntrA (rpoN) gene is required for diverse metabolic functions. Ronson, C.W., Nixon, B.T., Albright, L.M., Ausubel, F.M. J. Bacteriol. (1987) [Pubmed]
  9. Tandem DctD-binding sites of the Rhizobium meliloti dctA upstream activating sequence are essential for optimal function despite a 50- to 100-fold difference in affinity for DctD. Ledebur, H., Nixon, B.T. Mol. Microbiol. (1992) [Pubmed]
  10. Conservation between coding and regulatory elements of Rhizobium meliloti and Rhizobium leguminosarum dct genes. Jiang, J., Gu, B.H., Albright, L.M., Nixon, B.T. J. Bacteriol. (1989) [Pubmed]
  11. Analysis of the C4-dicarboxylate transport genes of Rhizobium meliloti: nucleotide sequence and deduced products of dctA, dctB, and dctD. Watson, R.J. Mol. Plant Microbe Interact. (1990) [Pubmed]
  12. Symbiotic loci of Rhizobium meliloti identified by random TnphoA mutagenesis. Long, S., McCune, S., Walker, G.C. J. Bacteriol. (1988) [Pubmed]
  13. Relationships between C4 dicarboxylic acid transport and chemotaxis in Rhizobium meliloti. Robinson, J.B., Bauer, W.D. J. Bacteriol. (1993) [Pubmed]
  14. Induction of C4-dicarboxylate transport genes by external stimuli in Rhizobium meliloti. Batista, S., Castro, S., Aguilar, O.M., Martínez-Drets, G. Can. J. Microbiol. (1992) [Pubmed]
  15. The ntrA gene of Agrobacterium tumefaciens: identification, cloning, and phenotype of a site-directed mutant. Wu, Z.L., Charles, T.C., Wang, H., Nester, E.W. J. Bacteriol. (1992) [Pubmed]
  16. Identification and sequence analysis of the Rhizobium meliloti dctA gene encoding the C4-dicarboxylate carrier. Engelke, T., Jording, D., Kapp, D., Pühler, A. J. Bacteriol. (1989) [Pubmed]
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