Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.13.3 (histidine kinase)
 2,405 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sinorhizobium meliloti participates in a nitrogen-fixing symbiosis with legume plant host species of the genera Medicago, Melilotus, and Trigonella. We recently identified an S. meliloti two-component sensory histidine kinase, CbrA, which is absolutely required to establish a successful symbiosis with Medicago sativa (K. E. Gibson, G. R. Campbell, J. Lloret, and G. C. Walker, J. Bacteriol. 188:4508-4521, 2006). In addition to having a symbiotic defect, the cbrA::Tn5 mutant also has free-living phenotypes that suggest a cell envelope perturbation. Because the bases for these phenotypes are not well understood, we undertook an identification of CbrA-regulated genes. We performed a microarray analysis and compared the transcriptome of the cbrA::Tn5 mutant to that of the wild type. Our global analysis of gene expression identified 162 genes that are differentially expressed in the cbrA::Tn5 mutant, including those encoding proteins involved in motility and chemotaxis, metabolism, and cell envelope function. With regard to those genes with a known role in symbiosis, we observed increased expression of nine genes with overlapping functions in bacterial invasion of its host, which suggests that the mutant could be competent for invasion. Since these CbrA-repressed genes are vital to the invasion process, it appears that down-regulation of CbrA activity is important at this stage of nodule development. In contrast, our previous work showed that CbrA is required for bacteria to establish themselves within the host as nitrogen-fixing symbionts. Therefore, we propose a model in which CbrA functions as a developmental switch during symbiosis.
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PMID:The symbiosis regulator CbrA modulates a complex regulatory network affecting the flagellar apparatus and cell envelope proteins. 1723 74

Spo0B is an important component of the phosphorelay signal transduction pathway, the pathway involved in the initiation of sporulation in Bacillus subtilis. Bioinformatic, phylogenetic and biochemical studies showed that Spo0B of Bacillus anthracis has evolved from citrate/malate kinases. During the course of evolution, Spo0B has retained the characteristic histidine kinase boxes H, N, F, G(1) and G(2), and has acquired nucleotide-binding domains, Walker A and Walker B, of ATPases. Owing to the presence of these domains, autophosphorylation and ATPase activity was observed in Spo0B of B. anthracis. Mutational studies showed that among the six histidine residues, His13 of the H-box is involved in the autophosphorylation activity of Spo0B, whereas Lys33 of the Walker A domain is associated with the ATPase activity of the protein. Thermodynamic and binding studies of the binding of Mg-ATP to Spo0B using isothermal titration calorimetry (ITC) suggested that the binding is driven by favorable entropy changes and that the reaction is exothermic, with an apparent dissociation constant (K(d)) equal to 0.02 mm. The value of the dissociation constant (K(d) = 0.05 mm) determined by the intrinsic fluorescence of trytophan of Spo0B was similar to that obtained by ITC studies. The purified Spo0B of B. anthracis also showed nucleoside diphosphate kinase-like activity of phosphate transfer from nucleoside triphosphate to nucleoside diphosphate. This is the first evidence for Spo0B of B. anthracis as an enzyme with histidine kinase and ATPase activities, which may have important roles to play in sporulation and pathogenesis.
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PMID:Spo0B of Bacillus anthracis - a protein with pleiotropic functions. 1819 May 31