Ion binding and selectivity of the rotor ring of the Na+-transporting V-ATPase.

DOI: 10.1073/pnas.0800992105

Authors: Takeshi Murata (Japan Science and Technology Agency) , Ichiro Yamato (Tokyo University of Science) , Yoshimi Kakinuma (Ehime University) , Mikako Shirouzu (Protein Research Group, RIKEN Genomic Sciences Center) , John E. Walker (Medical Research Council) , Shigeyuki Yokoyama (Protein Research Group, RIKEN Genomic Sciences Center) , So Iwata (Japan Science and Technology Agency; Protein Research Group, RIKEN Genomic Sciences Center)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 105 (25) , PAGES 8607-8612

State: Published (Approved)
Published: April 2008

Abstract: 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 Å 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.

Journal Keywords: Membrane Protein; Rotary Motor; X-Ray Crystallography; Lithium Ion; Enterococcus Hirae

Subject Areas: Biology and Bio-materials


Instruments: NONE-No attached Diamond beamline

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