title: Characterization of the nodulation plasmid encoded chemoreceptor gene mcpG from Rhizobium leguminosarum.
abstract: BACKGROUND
  In general, chemotaxis in Rhizobium has not been well characterized. Methyl accepting chemotaxis proteins are sensory proteins important in chemotaxis of numerous bacteria, but their involvement in Rhizobium chemotaxis is unclear and merits further investigation.
  
  
  RESULTS
  A putative methyl accepting chemotaxis protein gene (mcpG) of Rhizobium leguminosarum VF39SM was isolated and characterized. The gene was found to reside on the nodulation plasmid, pRleVF39d. The predicted mcpG ORF displayed motifs common to known methyl-accepting chemotaxis proteins, such as two transmembrane domains and high homology to the conserved methylation and signaling domains of well-characterized MCPs. Phenotypic analysis of mcpG mutants using swarm plates did not identify ligands for this putative receptor. Additionally, gene knockouts of mcpG did not affect a mutant strain's ability to compete for nodulation with the wild type. Notably, mcpG was found to be plasmid-encoded in all strains of R. leguminosarum and R. etli examined, though it was found on the nodulation plasmid only in a minority of strains.
  
  
  CONCLUSIONS
  Based on sequence homology R. leguminosarum mcpG gene codes for a methyl accepting chemotaxis protein. The gene is plasmid localized in numerous Rhizobium spp. Although localized to the sym plasmid of VF39SM mcpG does not appear to participate in early nodulation events. A ligand for McpG remains to be found. Apparent McpG orthologs appear in a diverse range of proteobacteria. Identification and characterization of mcpG adds to the family of mcp genes already identified in this organism.
authors.affiliation: Department of Biological Sciences, University of Calgary, Alberta, Canada, T2N 1N4. ckjost@yahoo.com
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Yost
authors.forename: Kirsten T
authors.initials: KT
authors.lastname: Clark
authors.forename: Kate L
authors.initials: KL
authors.lastname: Del Bel
authors.forename: Michael F
authors.initials: MF
authors.lastname: Hynes
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002628:Chemoreceptor Cells; D003001:Cloning, Molecular; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D000072236:Methyl-Accepting Chemotaxis Proteins; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010957:Plasmids / Q000235:genetics; D016961:Rhizobium leguminosarum / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins