Title | Ion binding and selectivity of the rotor ring of the Na+-transporting V-ATPase. |
Publication Type | Journal Article |
Year of Publication | 2008 |
Authors | Murata, T, Yamato, I, Kakinuma, Y, Shirouzu, M, Walker, JE, Yokoyama, S, Iwata, S |
Journal | Proc Natl Acad Sci U S A |
Volume | 105 |
Issue | 25 |
Pagination | 8607-12 |
Date Published | 2008 Jun 24 |
ISSN | 1091-6490 |
Keywords | Binding Sites, Biological Transport, Cations, Crystallography, X-Ray, Enterococcus, Kinetics, Lithium, Models, Biological, Models, Molecular, Sodium, Vacuolar Proton-Translocating ATPases |
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 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. |
DOI | 10.1073/pnas.0800992105 |
Alternate Journal | Proc. Natl. Acad. Sci. U.S.A. |
Citation Key | 10.1073/pnas.0800992105 |
PubMed ID | 18559856 |
PubMed Central ID | PMC2438407 |
Grant List | MC_U105663150 / / Medical Research Council / United Kingdom |