Ion binding and selectivity of the rotor ring of the Na+-transporting V-ATPase
Ion binding and selectivity of the rotor ring of the Na+-transporting V-ATPase
复制标题
DOI：
10.1073/pnas.0800992105
复制
发表时间：
2008-06-24
影响因子：
11.1
通讯作者：
Iwata, So
中科院分区：
文献类型：
--
作者：
Murata, Takeshi;Yamato, Ichiro;Iwata, So
液泡型 ATP 酶（V-ATP 酶）是真核细胞各个细胞内区室中的质子泵。希拉肠球菌的原核 VATP 酶与真核酶密切相关，为研究 V-ATP 酶的离子易位提供了独特的机会，因为它运输 Na+ 离子，更容易通过 X 射线晶体学和放射性同位素实验检测到。 E. hirae V-ATP酶的纯化转子环（K环）以高亲和力结合每个K单体一个Na+离子，其被Li+或H+竞争性抑制，表明K环也可以结合这些离子。在 Li+ 存在的情况下，2.8 埃的 K 环结构也支持了这一发现。与从酶活性估计的 Na+ 易位速率相比，Na+ 与纯化 K 环的结合和解离速率极其缓慢，强烈表明与定子亚基（1 亚基）的相互作用对于 Na+ 与 K 环结合/释放至关重要。
The vacuole-type ATPases (V-ATPases) are proton pumps in various intracellular compartments of eukaryotic cells. Prokaryotic VATPase of Enterococcus hirae, closely related to the eukaryotic enzymes, provides a unique opportunity to study ion translocation by V-ATPases because it transports Na+ ions, which are easier to detect by x-ray crystallography and radioisotope experiments. The purified rotor ring (K-ring) of the E. hirae V-ATPase binds one Na+ ion per K-monomer with high affinity, which is competitively inhibited by Li+ or H+, suggesting that the K-ring can also bind these ions. This finding is also supported by the K-ring structure at 2.8 angstrom in the presence of Li+. Association and dissociation rates of the Na+ to and from the purified K-ring were extremely slow compared with the Na+ translocation rate estimated from the enzymatic activity, strongly suggesting that interaction with the stator subunit (1-subunit) is essential for Na+ binding to/release from the K-ring.