Characterization of Bacillus subtilis YfkE (ChaA): a calcium-specific Ca2+/H+ antiporter of the CaCA family
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- 作者：Makoto Fujisawa ; Yuko Wada ; Takahiro Tsuchiya and Masahiro Ito
- 关键词：Bacillus subtilis ; Ca2+/H+ antiporter ; CaCA family ; Transporter
- 刊名：Archives of Microbiology
- 出版年：2009
- 出版时间：August, 2009
- 年：2009
- 卷：191
- 期：8
- 页码：649-657
- 全文大小：474.8 KB
文摘
YfkE, a protein from Bacillus subtilis, exhibits homology to the Ca2+:Cation Antiporter (CaCA) Family. In a fluorescence-based assay of everted membrane vesicles prepared from Na+(Ca2+)/H+ antiporter-defective mutant Escherichia coli KNabc, YfkE exhibited robust Ca2+/H+ antiport activity, with a K m for Ca2+ estimated at 12.5 μM at pH 8.5 and 113 μM at pH 7.5. Neither Na+ nor K+ served as a substrate. Mg2+ also did not serve as a substrate, but inhibited the Ca2+/H+ antiporter activity. The Ca2+ transport capability of YfkE was also observed directly by transport assays in everted membrane vesicles using radiolabeled 45Ca2+. Transcriptional analysis from the putative yfkED operon using β-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 Ca2+ signaling in the sporulation or germination process in B. subtilis. ChaA is proposed as the designation for YfkE of B. subtilis.