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ヨコヤマ ケン
YOKOYAMA KEN
横山 謙 所属 京都産業大学 生命科学部 先端生命科学科 職種 教授 |
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| 言語種別 | 英語 |
| 発行・発表の年月 | 2008/07 |
| 形態種別 | 研究論文 |
| 査読 | 査読あり |
| 標題 | ATP hydrolysis and synthesis of a rotary motor V-ATPase from Thermus thermophilus |
| 執筆形態 | その他 |
| 掲載誌名 | JOURNAL OF BIOLOGICAL CHEMISTRY |
| 出版社・発行元 | AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC |
| 巻・号・頁 | 283(30),pp.20789-20796 |
| 著者・共著者 | Masahiro Nakano,Hiromi Imamura,Masashi Toei,Masatada Tamakoshi,Masasuke Yoshida,Ken Yokoyama |
| 概要 | Vacuolar-type H(+)-ATPase (V-ATPase) catalyzes ATP synthesis and hydrolysis coupled with proton translocation across membranes via a rotary motor mechanism. Here we report biochemical and biophysical catalytic properties of V-ATPase from Thermus thermophilus. ATP hydrolysis of V-ATPase was severely inhibited by entrapment of Mg-ADP in the catalytic site. In contrast, the enzyme was very active for ATP synthesis (similar to 70 s(-1)) with the K(m) values for ADP and phosphate being 4.7 +/- 0.5 and 460 +/- 30 mu M, respectively. Single molecule observation showed V-ATPase rotated in a 120 degrees stepwise manner, and analysis of dwelling time allowed the binding rate constant k(on) for ATP to be estimated (similar to 1.1 x 10(6) M(-1) s(-1)), which was much lower than the k(on) (= V(max)/K(m)) for ADP (similar to 1.4 x 10(7) M(-1) s(-1)). The slower kon ATP than kon ADP and strong Mg-ADP inhibition may contribute to prevent wasteful consumption of ATP under in vivo conditions when the proton motive force collapses. |
| DOI | 10.1074/jbc.M801276200 |
| ISSN | 0021-9258 |
| PMID | 18492667 |