title: Characterization of Bacillus subtilis YfkE (ChaA): a calcium-specific Ca2+/H+ antiporter of the CaCA family.
abstract: YfkE, a protein from Bacillus subtilis, exhibits homology to the Ca(2+):Cation Antiporter (CaCA) Family. In a fluorescence-based assay of everted membrane vesicles prepared from Na(+)(Ca(2+))/H(+) antiporter-defective mutant Escherichia coli KNabc, YfkE exhibited robust Ca(2+)/H(+) antiport activity, with a K (m) for Ca(2+) estimated at 12.5 muM at pH 8.5 and 113 muM at pH 7.5. Neither Na(+) nor K(+) served as a substrate. Mg(2+) also did not serve as a substrate, but inhibited the Ca(2+)/H(+) antiporter activity. The Ca(2+) transport capability of YfkE was also observed directly by transport assays in everted membrane vesicles using radiolabeled (45)Ca(2+). Transcriptional analysis from the putative yfkED operon using beta-garactosidase activity as a reporter revealed that both of the yfkE and yfkD genes are regulated by forespore-specific sigma factor, SigG, and the general stress response regulator, SigB. These results suggest that YfkE may be needed for Ca(2+) signaling in the sporulation or germination process in B. subtilis. ChaA is proposed as the designation for YfkE of B. subtilis.
authors: Bio-Nano Electronics Research Center, Toyo University, 2100, Kujirai, Kawagoe, Saitama, 350-8585, Japan.
authors: Makoto
authors: M
authors: Fujisawa
authors: Yuko
authors: Y
authors: Wada
authors: Takahiro
authors: T
authors: Tsuchiya
authors: Masahiro
authors: M
authors: Ito
mesh_terms: D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D009876:Operon; D012808:Sigma Factor / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D017920:Antiporters; D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D012808:Sigma Factor; C027614:calcium-hydrogen antiporters