Toyoshima Chikashi, Norimatsu Yoshiyuki, Iwasawa Shiho, Tsuda Takeo, Ogawa Haruo
Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
Proc Natl Acad Sci U S A. 2007 Dec 11;104(50):19831-6. doi: 10.1073/pnas.0709978104. Epub 2007 Dec 5.
Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum is the best-studied member of the P-type or E1/E2 type ion transporting ATPases. It has been crystallized in seven different states that cover nearly the entire reaction cycle. Here we describe the structure of this ATPase complexed with phosphate analogs BeF(3)(-) and AlF(4)(-) in the absence of Ca(2+), which correspond to the E2P ground state and E2 approximately P transition state, respectively. The luminal gate is open with BeF(3)(-) and closed with AlF(4)(-). These and the E1 approximately P.ADP analog crystal structures show that a two-step rotation of the cytoplasmic A-domain opens and closes the luminal gate through the movements of the M1-M4 transmembrane helices. There are several conformational switches coupled to the rotation, and the one in the cytoplasmic part of M2 has critical importance. In the second step of rotation, positioning of one water molecule couples the hydrolysis of aspartylphosphate to closing of the gate.
骨骼肌肌浆网的Ca(2+)-ATP酶是P型或E1/E2型离子转运ATP酶中研究最为深入的成员。它已在七种不同状态下结晶，这些状态几乎涵盖了整个反应周期。在此，我们描述了该ATP酶在无Ca(2+)情况下与磷酸类似物BeF(3)(-)和AlF(4)(-)复合的结构，它们分别对应于E2P基态和E2近似P过渡态。与BeF(3)(-)结合时腔门打开，与AlF(4)(-)结合时腔门关闭。这些以及E1近似P.ADP类似物晶体结构表明，细胞质A结构域的两步旋转通过M1 - M4跨膜螺旋的运动打开和关闭腔门。有几个构象转换与旋转相关联，其中M2细胞质部分的构象转换至关重要。在旋转的第二步中，一个水分子的定位将天冬氨酰磷酸的水解与腔门的关闭耦合起来。
