Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark.
Proc Natl Acad Sci U S A. 2010 Dec 14;107(50):21400-5. doi: 10.1073/pnas.1010416107. Epub 2010 Nov 22.
The activity of P-type plasma membrane H(+)-ATPases is modulated by H(+) and cations, with K(+) and Ca(2+) being of physiological relevance. Using X-ray crystallography, we have located the binding site for Rb(+) as a K(+) congener, and for Tb(3+) and Ho(3+) as Ca(2+) congeners. Rb(+) is found coordinated by a conserved aspartate residue in the phosphorylation domain. A single Tb(3+) ion is identified positioned in the nucleotide-binding domain in close vicinity to the bound nucleotide. Ho(3+) ions are coordinated at two distinct sites within the H(+)-ATPase: One site is at the interface of the nucleotide-binding and phosphorylation domains, and the other is in the transmembrane domain toward the extracellular side. The identified binding sites are suggested to represent binding pockets for regulatory cations and a H(+) binding site for protons leaving the pump molecule. This implicates Ho(3+) as a novel chemical tool for identification of proton binding sites.
P 型质膜 H(+)-ATP 酶的活性受 H(+)和阳离子调节，其中 K(+)和 Ca(2+)与生理学相关。我们使用 X 射线晶体学将 Rb(+)的结合位点定位为 K(+)的同系物，将 Tb(3+)和 Ho(3+)的结合位点定位为 Ca(2+)的同系物。Rb(+)由磷酸化结构域中的保守天冬氨酸残基配位。一个 Tb(3+)离子被鉴定位于核苷酸结合结构域内，靠近结合的核苷酸。Ho(3+)离子在 H(+)-ATP 酶内的两个不同位点被配位：一个位点在核苷酸结合和磷酸化结构域的界面处，另一个位点在朝向细胞外的跨膜结构域中。鉴定出的结合位点被认为是调节阳离子的结合口袋和质子离开泵分子的 H(+)结合位点。这表明 Ho(3+)是鉴定质子结合位点的新型化学工具。
