Tsuda Takeo, Toyoshima Chikashi
Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo, Japan.
EMBO J. 2009 Jun 17;28(12):1782-91. doi: 10.1038/emboj.2009.143. Epub 2009 May 28.
Heavy metal pumps constitute a large subgroup in P-type ion-transporting ATPases. One of the outstanding features is that the nucleotide binding N-domain lacks residues critical for ATP binding in other well-studied P-type ATPases. Instead, they possess an HP-motif and a Gly-rich sequence in the N-domain, and their mutations impair ATP binding. Here, we describe 1.85 A resolution crystal structures of the P- and N-domains of CopA, an archaeal Cu(+)-transporting ATPase, with bound nucleotides. These crystal structures show that CopA recognises the adenine ring completely differently from other P-type ATPases. The crystal structure of the His462Gln mutant, in the HP-motif, a disease-causing mutation in human Cu(+)-ATPases, shows that the Gln side chain mimics the imidazole ring, but only partially, explaining the reduction in ATPase activity. These crystal structures lead us to propose a role of the His and a mechanism for removing Mg(2+) from ATP before phosphoryl transfer.
重金属泵是P型离子转运ATP酶中的一个大亚组。其突出特点之一是，在其他经过充分研究的P型ATP酶中，核苷酸结合N结构域缺乏对ATP结合至关重要的残基。相反，它们在N结构域中具有一个HP基序和一个富含甘氨酸的序列，并且它们的突变会损害ATP结合。在这里，我们描述了古铜离子转运ATP酶CopA的P结构域和N结构域与结合核苷酸的分辨率为1.85埃的晶体结构。这些晶体结构表明，CopA识别腺嘌呤环的方式与其他P型ATP酶完全不同。HP基序中的His462Gln突变体的晶体结构（人类铜离子ATP酶中的一种致病突变）表明，谷氨酰胺侧链仅部分模拟了咪唑环，这解释了ATP酶活性的降低。这些晶体结构使我们提出了组氨酸的作用以及在磷酸转移之前从ATP中去除镁离子的机制。
