P-型ATP酶是对所有真核生物和很多原核生物具有根本重要性的阳离子泵。本期Nature上3篇论文介绍了关于这一超级家族关键成员的结构及功能研究。本期封面所示为钠离子和钾离子泵的结构，是由Morth等人在本期杂志上以3.5埃的分辨率描述的，同时还刊登了J. C. Skou关于其50年前发现依赖于钠离子和钾离子的ATP酶活性的原始笔记。这篇论文显示了ATP酶与钾相结合的状态，同时还暗示了一种依赖于电压的调控基础。这些结果部分是通过与Skou所作实验相似的动能实验获得的。Olesen等人介绍了肌质网Ca2+-ATP酶(钙泵)的新的晶体结构，同时还有关于功能的研究工作，并且最终呈现了关于钙运输的一个完整机制。在植物和真菌中，细胞离子平衡状态和膜势是由胞质膜H+-ATP酶(另一种P-型ATP酶)提供动力的。Pedersen等人介绍了它的X-射线结构，提供了关于它是如何沿一个陡峭的电化学梯度来泵输质子的有关线索。
原始出处:
Nature 450, 1036-1042 (13 December 2007) | doi:10.1038/nature06418; Received 13 August 2007; Accepted 26 October 2007
The structural basis of calcium transport by the calcium pump
Claus Olesen1,2, Martin Picard3,4, Anne-Marie Lund Winther1,3, Claus Gyrup3, J. Preben Morth1,3, Claus Oxvig3, Jesper Vuust Møller1,2 & Poul Nissen1,3
Centre for Membrane Pumps in Cells and Disease—PUMPKIN, Danish National Research Foundation, and,
Institute of Physiology and Biophysics, University of Aarhus, Ole Worms Alle, blg. 1185, DK - 8000 Aarhus C, Denmark
Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, DK - 8000 Aarhus C, Denmark
Present address: Laboratoire de Cristallographie et RMN biologiques, UMR 8015 CNRS, Faculté de Pharmacie. Université Paris Descartes, 4 avenue de l'Observatoire, 75270 Paris Cedex 06, France.
Correspondence to: Jesper Vuust Møller1,2Poul Nissen1,3 Correspondence and requests for materials should be addressed to P.N. (Email: pn@mb.au.dk) and J.V.M. (Email: jvm@biophys.au.dk).
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Abstract
The sarcoplasmic reticulum Ca2+-ATPase, a P-type ATPase, has a critical role in muscle function and metabolism. Here we present functional studies and three new crystal structures of the rabbit skeletal muscle Ca2+-ATPase, representing the phosphoenzyme intermediates associated with Ca2+ binding, Ca2+ translocation and dephosphorylation, that are based on complexes with a functional ATP analogue, beryllium fluoride and aluminium fluoride, respectively. The structures complete the cycle of nucleotide binding and cation transport of Ca2+-ATPase. Phosphorylation of the enzyme triggers the onset of a conformational change that leads to the opening of a luminal exit pathway defined by the transmembrane segments M1 through M6, which represent the canonical membrane domain of P-type pumps. Ca2+ release is promoted by translocation of the M4 helix, exposing Glu 309, Glu 771 and Asn 796 to the lumen. The mechanism explains how P-type ATPases are able to form the steep electrochemical gradients required for key functions in eukaryotic cells.
