P-型ATP酶是對所有真核生物和很多原核生物具有根本重要性的陽離子泵。本期Nature上3篇論文介紹了關於這一超級家族關鍵成員的結構及功能研究。本期封面所示為鈉離子和鉀離子泵的結構，是由Morth等人在本期雜誌上以3.5埃的解析度描述的，同時還刊登了J. C. Skou關於其50年前發現依賴於鈉離子和鉀離子的ATP酶活性的原始筆記。這篇論文顯示了ATP酶與鉀相結合的狀態，同時還暗示了一種依賴於電壓的調控基礎。這些結果部分是通過與Skou所作實驗相似的動能實驗獲得的。Olesen等人介紹了肌質網Ca2+-ATP酶(鈣泵)的新的晶體結構，同時還有關於功能的研究工作，並且最終呈現了關於鈣運輸的一個完整機制。在植物和真菌中，細胞離子平衡狀態和膜勢是由胞質膜H+-ATP酶(另一種P-型ATP酶)提供動力的。Pedersen等人介紹了它的X-射線結構，提供了關於它是如何沿一個陡峭的電化學梯度來泵輸質子的有關線索。
原始出處:
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
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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of pageThe 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.