Structural identification of cation binding pockets in the plasma membrane proton pump

Kira Ekberg, Bjørn P Pedersen, Danny Mollerup Sørensen, Ann Kallehauge Nielsen, Bjarke Veierskov, Poul Nissen, Michael G Palmgren, Morten Jeppe Buch-Pedersen

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Abstract

The activity of P-type plasma membrane H(+)-ATPases is modulated by H(+) and cations, with K(+) and Ca(2+) being of physiological relevance. Using X-ray crystallography, we have located the binding site for Rb(+) as a K(+) congener, and for Tb(3+) and Ho(3+) as Ca(2+) congeners. Rb(+) is found coordinated by a conserved aspartate residue in the phosphorylation domain. A single Tb(3+) ion is identified positioned in the nucleotide-binding domain in close vicinity to the bound nucleotide. Ho(3+) ions are coordinated at two distinct sites within the H(+)-ATPase: One site is at the interface of the nucleotide-binding and phosphorylation domains, and the other is in the transmembrane domain toward the extracellular side. The identified binding sites are suggested to represent binding pockets for regulatory cations and a H(+) binding site for protons leaving the pump molecule. This implicates Ho(3+) as a novel chemical tool for identification of proton binding sites.
OriginalsprogEngelsk
TidsskriftProceedings of the National Academy of Sciences
Vol/bind107
Nummer50
Sider (fra-til)21400-5
Antal sider6
ISSN0027-8424
DOI
StatusUdgivet - 2010

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