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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structural role of countertransport revealed in Ca(2+) pump crystal structure in the absence of Ca(2+).
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Structural role of countertransport revealed in Ca(2+) pump crystal structure in the absence of Ca(2+).

机译：在没有Ca（2+）的Ca（2+）泵晶体结构中揭示的反转运的结构作用。

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摘要

Ca(2+)-ATPase of sarcoplasmic reticulum is an ATP-powered Ca(2+) pump but also a H(+) pump in the opposite direction with no demonstrated functional role. Here, we report a 2.4-A-resolution crystal structure of the Ca(2+)-ATPase in the absence of Ca(2+) stabilized by two inhibitors, dibutyldihydroxybenzene, which bridges two transmembrane helices, and thapsigargin, also bound in the membrane region. Now visualized are water and several phospholipid molecules, one of which occupies a cleft between two transmembrane helices. Atomic models of the Ca(2+) binding sites with explicit hydrogens derived by continuum electrostatic calculations show how water and protons fill the space and compensate charge imbalance created by Ca(2+)-release. They suggest that H(+) countertransport is a consequence of a requirement for maintaining structural integrity of the empty Ca(2+)-binding sites. For this reason, cation countertransport is probably mandatory for all P-type ATPases and possibly accompanies transport of water as well.
机译：肌质网的Ca（2 +）-ATPase是由ATP驱动的Ca（2+）泵，但在相反的方向上也具有H（+）泵，未显示功能性作用。在这里，我们报告的Ca（2 +）-ATPase的2.4-A分辨率晶体结构不存在由两种抑制剂稳定的Ca（2+），二丁基二羟基苯桥接了两个跨膜螺旋和thapsigargin，也结合在膜区域。现在可以看到水和几个磷脂分子，其中一个分子位于两个跨膜螺旋之间的缝隙中。通过连续静电计算得出的具有明确氢原子的Ca（2+）结合位点的原子模型表明水和质子如何填充空间并补偿由Ca（2+）释放产生的电荷不平衡。他们建议H（+）反转运是维持空Ca（2+）结合位点的结构完整性的要求的结果。因此，阳离子反转运可能对所有P型ATP酶都是必不可少的，并且还可能伴随水的运输。

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