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EMBO J. 2009 Jun 3;28(11):1637-43. doi: 10.1038/emboj.2009.102. Epub 2009 Apr 23.

Inter-subunit interaction of gastric H+,K+-ATPase prevents reverse reaction of the transport cycle.

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  • 1Department of Biophysics, Faculty of Science, Kyoto University, Kyoto, Japan.


The gastric H(+),K(+)-ATPase is an ATP-driven proton pump responsible for generating a million-fold proton gradient across the gastric membrane. We present the structure of gastric H(+),K(+)-ATPase at 6.5 A resolution as determined by electron crystallography of two-dimensional crystals. The structure shows the catalytic alpha-subunit and the non-catalytic beta-subunit in a pseudo-E(2)P conformation. Different from Na(+),K(+)-ATPase, the N-terminal tail of the beta-subunit is in direct contact with the phosphorylation domain of the alpha-subunit. This interaction may hold the phosphorylation domain in place, thus stabilizing the enzyme conformation and preventing the reverse reaction of the transport cycle. Indeed, truncation of the beta-subunit N-terminus allowed the reverse reaction to occur. These results suggest that the beta-subunit N-terminus prevents the reverse reaction from E(2)P to E(1)P, which is likely to be relevant for the generation of a large H(+) gradient in vivo situation.

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