Harada M, Ito Y, Sato M, Aono O, Ohta S, Kagawa Y
Institute for Solid State Physics, University of Tokyo, Japan.
J Biol Chem. 1991 Jun 25;266(18):11455-60.
The alpha 3 beta 3 complex of ATP synthase obtained from a thermophilic bacterium PS3 was isolated and found to show the ATPase activity (Kagawa, Y., Ohta, S., and Otawara-Hamamoto, Y. (1989) FEBS Lett. 249, 67-69). The structure and the nucleotide binding effects of the alpha 3 beta 3 complex were investigated by means of small-angle x-ray scattering and high performance liquid chromatography. The scattering profile from the alpha 3 beta 3 complex was explained with a model in which the complex is made of an ellipsoid of revolution with the axes of 121.8, 121.8, and 72.0 A having an elliptical hollow cavity with the axes of 35.4, 35.4, and 72.0 A. By the addition of Mg.AT(D)P, significant changes in the scattering profile were observed, in which the radius of gyration decreased from 44 to 35 A. This change was found by gel filtration to be caused by the dissociation reaction from the alpha 3 beta 3 hexamer to the alpha beta dimer. The dissociation of the alpha 3 beta 3 complex was not induced by unhydrolyzable ATP analogue, nor by Pi, Mg2+, and Pi + Mg2+. The structure of the dimer was well explained by the triaxial ellipsoidal model with the axes of 105.2, 39.4, and 108.2 A. The dissociation into the dimer is considered to be related to the ATPase activity because the AT(D)P-induced dissociation is observed only in the presence of Mg2+ ions.
从嗜热细菌PS3中分离出ATP合酶的α3β3复合体，发现其具有ATP酶活性（Kagawa, Y., Ohta, S., and Otawara-Hamamoto, Y. (1989) FEBS Lett. 249, 67 - 69）。通过小角X射线散射和高效液相色谱法研究了α3β3复合体的结构和核苷酸结合效应。α3β3复合体的散射图谱可以用一个模型来解释，该模型中复合体由一个旋转椭球体组成，其轴长分别为121.8、121.8和72.0 Å，内部有一个椭圆形空洞，轴长分别为35.4、35.4和72.0 Å。加入Mg·AT(D)P后，散射图谱发生了显著变化，其中回转半径从44 Å减小到35 Å。通过凝胶过滤发现这种变化是由α3β3六聚体解离为αβ二聚体的反应引起的。不可水解的ATP类似物、Pi、Mg2+以及Pi + Mg2+均未诱导α3β3复合体的解离。二聚体的结构可以用一个三轴椭球模型很好地解释，其轴长分别为105.2、39.4和108.2 Å。解离为二聚体被认为与ATP酶活性有关，因为只有在Mg2+离子存在的情况下才会观察到AT(D)P诱导的解离。
