The C-terminal receiver domain of the Rhizobium leguminosarum bv. viciae FixL protein is required for free-living microaerobic induction of the fnrN promoter.
The Rhizobium leguminosarum bv. viciae VF39 FixL protein belongs to a distinct group of hybrid regulatory sensor proteins that bear a covalently linked C-terminal receiver domain. FixL has an unorthodox histidine kinase domain, which is shared with many other hybrid regulators. The purified FixL protein had autophosphorylation activity. A truncated protein, lacking the receiver domain, had a much-reduced autophosphorylation activity. However, this truncated protein still efficiently phosphorylated the purified receiver domain in trans. This indicates that, in the full-length FixL protein, the conserved histidine residue in the kinase domain is phosphorylated only transiently and that most of the phosphoryl label accumulates in the C-terminal receiver domain. Gene-fusion studies showed that the fixL gene is required for free-living microaerobic induction of the fnrN promoter. The presence of a functional fixK gene is not required. An R. leguminosarum strain lacking fixL could not be complemented with a truncated copy of the gene lacking the receiver domain. This indicates that the C-terminal receiver domain is an intermediate in the signal transduction pathway that links oxygen limitation to induction of the fnrN promoter in R. leguminosarum bv. viciae VF39.
Boesten
Bert
B
Ökologie des Bodens, Botanisches Institut, RWTH-Aachen, Worringerweg 1, 52056 Aachen, Germany.
Priefer
Ursula B
UB
Ökologie des Bodens, Botanisches Institut, RWTH-Aachen, Worringerweg 1, 52056 Aachen, Germany.
D000222:Adaptation, Physiological / Q000235:genetics; D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D006420:Hemeproteins / Q000235:genetics / Q000378:metabolism*; D000071677:Histidine Kinase; D010100:Oxygen / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016961:Rhizobium leguminosarum / Q000235:genetics* / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*
D001426:Bacterial Proteins; C095881:FnrN protein, Rhizobium leguminosarum; D006420:Hemeproteins; D014157:Transcription Factors; C066628:FixK protein, Bacteria; D011494:Protein Kinases; C067929:FixL protein, Bacteria; D000071677:Histidine Kinase; D005966:Glucuronidase; D010100:Oxygen