文章基本信息

标题：Ion binding and selectivity of the rotor ring of the Na+-transporting V-ATPase
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作者：Takeshi Murata ; Ichiro Yamato ; Yoshimi Kakinuma 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2008
卷号：105
期号：25
页码：8607-8612
DOI：10.1073/pnas.0800992105
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The vacuole-type ATPases (V-ATPases) are proton pumps in various intracellular compartments of eukaryotic cells. Prokaryotic V-ATPase 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 A 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 (I-subunit) is essential for Na+ binding to /release from the K-ring.
关键词：membrane protein ; rotary motor ; x-ray crystallography ; lithium ion ; Enterococcus hirae