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Ion binding and selectivity of the rotor ring of the Na+-transporting V-ATPase.
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
Added On:
19/08/2009 23:07
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