Haupt Melina, Bramkamp Marc, Coles Murray, Kessler Horst, Altendorf Karlheinz
Institut für Organische Chemie und Biochemie, Technische Universität Munchen, Garching, Germany.
J Mol Microbiol Biotechnol. 2005;10(2-4):120-31. doi: 10.1159/000091559.
P-type ATPases are amongst the most abundant enzymes that are responsible for active transport of ions across biological membranes. Within the last 5 years a detailed picture of the structure and function of these transport ATPases has emerged. Here, we report on the recent progress in elucidating the molecular mechanism of a unique, prokaryotic member of P-type ATPases, the Kdp-ATPase. The review focuses on the catalytic parts of the central subunit, KdpB. The structure of the nucleotide-binding domain was solved by NMR spectroscopy at high resolution and a model of the nucleotide-binding mode was presented. The nucleotide turned out to be 'clipped' into the binding pocket by a pi-pi interaction to F377 on one side and a cation-pi interaction to K395 on the other. The 395KGXXD/E motif and thus the nucleotide-binding mode seems to be conserved in all P-type ATPases, except the heavy metal-transporting (class IB) ATPases. Hence, it can be concluded that KdpB is currently misgrouped as class IA. Mutational studies on two highly conserved residues (D583 and K586) in the transmembrane helix 5 of KdpB revealed that they are indispensable in coupling ATP hydrolysis to ion translocation. Based on these results, two possible pathways for the reaction cycle are discussed.
P型ATP酶是负责离子跨生物膜主动运输的最丰富的酶之一。在过去5年里，这些运输ATP酶的结构和功能的详细情况已逐渐明晰。在此，我们报告在阐明P型ATP酶中一种独特的原核成员——Kdp - ATP酶的分子机制方面的最新进展。本综述聚焦于中心亚基KdpB的催化部分。通过核磁共振光谱高分辨率解析了核苷酸结合结构域的结构，并提出了核苷酸结合模式的模型。结果表明，核苷酸通过一侧与F377的π-π相互作用以及另一侧与K395的阳离子-π相互作用“夹入”结合口袋。除重金属运输（IB类）ATP酶外，395KGXXD/E基序以及核苷酸结合模式似乎在所有P型ATP酶中都是保守的。因此，可以得出结论，KdpB目前被错误地归类为IA类。对KdpB跨膜螺旋5中两个高度保守残基（D583和K586）的突变研究表明，它们在将ATP水解与离子转运偶联中是不可或缺的。基于这些结果，讨论了反应循环的两种可能途径。
