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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 | 1989 |
| 形態種別 | 研究論文 |
| 査読 | 査読あり |
| 標題 | The reconstituted α3β3δ complex of the thermostable F1-ATPase |
| 執筆形態 | その他 |
| 掲載誌名 | Journal of Biological Chemistry |
| 巻・号・頁 | 264(36),pp.21837-21841 |
| 著者・共著者 | K. Yokoyama,T. Hisabori,M. Yoshida |
| 概要 | Previously we reported that ATPase activity was recovered when the subunit α + β + γ or α + β + δ of the F1-ATPase from the thermophilic bacterium PS3 were combined under appropriate conditions. Unlike that of holoenzyme (TF1) and the α + β + γ mixture, ATPase activity of the α + β + δ mixture was heat labile and insensitive to azide inhibition (Yoshida, M., Sone, N., Hirata, H., and Kagawa, Y. (1977) J. Biol. Chem. 252, 3480-3485). Here, the properties of purified subunit complexes were compared in detail with those of native TF1. The subunit stoichiometries OF the complexes were determined to be α3β3γ1 and α3β3δ1. In general, the properties of the α3β3γ complex are very similar to those of TF1, whereas those of the α3β3δ complex are significantly different ATPase activity of the α3β3δ complex is cold labile. The α3β3δ complex showed a less stringent specificity for substrate and divalent cation than TF1 and the α3β3γ complex. Two K(m) values for ATP were exhibited by the α3β3δ complex with the lower one being in the range of 0.1 μM. Equilibrium dialysis experiments revealed that the α3β3δ complex cannot specifically bind ADP in the absence of Mg2+, while TF1 and the α3β3γ complex bind about 1 and 3 mol of ADP/mol of enzyme, respectively. ADP-dependent inactivation of the α3β3δ complex by dicyclohexylcarbodiimide was not observed. The α3β3δ complex was readily formed when the γ subunit was added to the α3β3δ complex, suggesting that the α3β3δ complex is not a 'dead-end' complex. The cause of thermolability of the α3β3δ complex appears to be the low stability of the complex itself at high temperature and not due to an unusually low thermostability of the δ subunit |
| ISSN | 0021-9258 |
| PMID | 2532213 |