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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 | 2013/01 |
| 形態種別 | 研究論文 |
| 査読 | 査読あり |
| 標題 | Mechanical Modulation of ATP-binding Affinity of V-1-ATPase |
| 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 | 288(1),pp.619-623 |
| 著者・共著者 | Naciye Esma Tirtom,Daichi Okuno,Masahiro Nakano,Ken Yokoyama,Hiroyuki Noji |
| 概要 | V-1-ATPase is a rotary motor protein that rotates the central shaft in a counterclockwise direction hydrolyzing ATP. Although the ATP-binding process is suggested to be the most critical reaction step for torque generation in F-1-ATPase (the closest relative of V-1-ATPase evolutionarily), the role of ATP binding for V-1-ATPase in torque generation has remained unclear. In the present study, we performed single-molecule manipulation experiments on V-1-ATPase from Thermus thermophilus to investigate how the ATP-binding process is modulated upon rotation of the rotary shaft. When V-1-ATPase showed an ATP-waiting pause, it was stalled at a target angle and then released. Based on the response of the V-1-ATPase released, the ATP-binding probability was determined at individual stall angles. It was observed that the rate constant of ATP binding (k(on)) was exponentially accelerated with forward rotation, whereas the rate constant of ATP release (k(off)) was exponentially reduced. The angle dependence of the k(off) of V-1-ATPase was significantly smaller than that of F-1-ATPase, suggesting that the ATP-binding process is not the major torque-generating step in V-1-ATPase. When V-1-ATPase was stalled at the mean binding angle to restrict rotary Brownian motion, k(on) was evidently slower than that determined from free rotation, showing the reaction rate enhancement by conformational fluctuation. It was also suggested that shaft of V-1-ATPase should be rotated at least 277 degrees in a clockwise direction for efficient release of ATP under ATP-synthesis conditions. |
| DOI | 10.1074/jbc.M112.420729 |
| ISSN | 0021-9258 |
| PMID | 23155048 |