Bianchet M, Ysern X, Hullihen J, Pedersen P L, Amzel L M
Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
J Biol Chem. 1991 Nov 5;266(31):21197-201.
The F1 moiety of the mitochondrial ATP synthase is composed of five different subunits with stoichiometry alpha 3 beta 3 gamma delta epsilon and exhibits the capacity to synthesize ATP from ADP and Pi. We have previously crystallized rat liver F1 and described its structure at 9-A resolution (Amzel, L. M., McKinney, M., Narayanan, P., and Pedersen, P. L. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 5852-5856). Here we present an x-ray map of this complex enzyme at 3.6 A, which provides a much more informative description of its quaternary structure. The overall dimensions of the F1 molecule are 120 A x 120 A x 74 A. The enzyme exhibits 3-fold symmetry relating the three copies of each of the two major subunits, alpha and beta. As the alpha subunits (but not the beta subunits) contain cysteine residues, it has been possible to identify the alpha subunits by heavy atom labeling with mersalyl and to relate their positions in the F1 molecule to the beta subunits. Significantly, the alpha and beta subunits each exist as trimeric arrays which are organized in two slightly offset, interdigitated layers along the 3-fold axis. In one trimeric layer the alpha subunits are located close to the axis with homologous subunits interacting with each other; in the other trimeric layer the beta subunits are far from the axis, and they interact only with alpha subunits and not with one another. At one end of the structure, part of the interface between each alpha and beta subunit encloses a space or "pocket" that is accessible to the solvent; at the other end the interfaces between the subunits are more open and exposed. The present work represents the highest resolution map reported to date for the F1 moiety of an ATP synthase complex.
线粒体ATP合酶的F1部分由五个不同的亚基组成，化学计量比为α3β3γδε，具有从ADP和Pi合成ATP的能力。我们之前已使大鼠肝脏F1结晶，并以9埃的分辨率描述了其结构（阿姆泽尔，L.M.，麦金尼，M.，纳拉亚南，P.，和佩德森，P.L.（1982年）《美国国家科学院院刊》79，5852 - 5856）。在此，我们展示了该复合酶在3.6埃分辨率下的X射线图谱，这为其四级结构提供了更丰富的信息描述。F1分子的整体尺寸为120埃×120埃×74埃。该酶表现出三重对称性，将两个主要亚基α和β的每个三个拷贝联系起来。由于α亚基（而非β亚基）含有半胱氨酸残基，因此可以通过用汞撒利进行重原子标记来鉴定α亚基，并将它们在F1分子中的位置与β亚基相关联。值得注意的是，α和β亚基各自以三聚体阵列形式存在，它们沿着三重轴排列在两个略有偏移、相互交错的层中。在一个三聚体层中，α亚基位于靠近轴的位置，同源亚基相互作用；在另一个三聚体层中，β亚基远离轴，它们仅与α亚基相互作用，彼此之间不相互作用。在结构的一端，每个α和β亚基之间的部分界面围成一个可被溶剂接触的空间或“口袋”；在另一端，亚基之间的界面更开放且暴露。目前的工作代表了迄今为止报道的ATP合酶复合物F1部分的最高分辨率图谱。
