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

• Published in: Proceedings of the National Academy of Sciences - PNAS 2010-12, Vol.107 (50), p.21400-21405
• Main Authors: Ekberg, Kira, Pedersen, Bjørn P., Sørensen, Danny M., Nielsen, Ann K., Veierskov, Bjarke, Nissen, Poul, Palmgren, Michael G., Buch-Pedersen, Morten J., Petsko, Gregory A.
• Format: Article
• Language: English
• Subjects: Adenosine triphosphatase; Adenosine triphosphatases; Binding Sites; Biological Sciences; Calcium; Cations - chemistry; Cell Membrane - chemistry; Cell membranes; Cells; Crystallography, X-Ray; Genetic Complementation Test; Ions; Membranes; Metals - chemistry; Molecular Sequence Data; Molecular structure; Molecules; Nucleotides; Phosphorylation; Point Mutation; Protein Structure, Tertiary; Proteins; Proton Pumps - chemistry; Proton Pumps - genetics; Protons; Pumps; Saccharomyces cerevisiae; Yeasts
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1010416107

The activity of P-type plasma membrane H⁺-ATPases is modulated by H⁺ and cations, with K⁺ and Ca²⁺ being of physiological relevance. Using X-ray crystallography, we have located the binding site for Rb⁺ as a K⁺ congener, and for Tb³⁺ and Ho³⁺ as Ca²⁺ congeners. Rb⁺ is found coordinated by a conserved aspartate residue in the phosphorylation domain. A single Tb³⁺ ion is identified positioned in the nucleotide-binding domain in close vicinity to the bound nucleotide. Ho³⁺ 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 Ho³⁺ as a novel chemical tool for identification of proton binding sites.