title: Spo0B of Bacillus anthracis - a protein with pleiotropic functions.
abstract: 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.
authors.affiliation: Allergy and Infectious Diseases, Institute of Genomics and Integrative Biology, Delhi, India.
authors.forename: Abid R
authors.initials: AR
authors.lastname: Mattoo
authors.forename: Mohd
authors.initials: M
authors.lastname: Saif Zaman
authors.forename: Gyanendra P
authors.initials: GP
authors.lastname: Dubey
authors.forename: Amit
authors.initials: A
authors.lastname: Arora
authors.forename: Azeet
authors.initials: A
authors.lastname: Narayan
authors.forename: Noor
authors.initials: N
authors.lastname: Jailkhani
authors.forename: Kusum
authors.initials: K
authors.lastname: Rathore
authors.forename: Souvik
authors.initials: S
authors.lastname: Maiti
authors.forename: Yogendra
authors.initials: Y
authors.lastname: Singh
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D001408:Bacillus anthracis / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010766:Phosphorylation; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; C030069:spore-specific proteins, Bacillus; D000255:Adenosine Triphosphate