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bioRxiv · 10.1101/2021.11.08.467847

The beryllium fluoride form of the Na+,K+-ATPase and the intermediates of the functional cycle

Nissen, P.·Fruergaard, m. U.·Fedosova, N. U.·Andersen, J. L.·Shahsavar, A.·Quistgaard, E.·Poulsen, H.·Dach, I.
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Abstract

The Na+,K+-ATPase generates electrochemical gradients of Na+ and K+ across the plasma membrane. Here, we describe a 4.0 [A] resolution crystal structure of the pig kidney Na+,K+-ATPase stabilized by beryllium fluoride (denoted E2-BeFx). The structure shows high resemblance to the E2P phosphoenzyme obtained by phosphorylation from inorganic phosphate (Pi) and stabilised by cardiotonic steroids, and reveals a Mg2+ bound near the ion binding site II. Anomalous Fourier analysis of the crystals soaked in Rb+ (K+ congener) followed by a low resolution rigid-body refinement (6.9-7.5 [A]) revealed pre-occlusion transitions leading to activation of the desphosphorylation reaction. Mg2+ location indicates a site of an initial K+ recognition and acceptance upon binding to the outward-open E2P state after Na+ release. Despite the overall structural resemblance to the Pi-induced E2P phosphoform, BeFx inhibited enzyme is able to bind both ADP/ATP and ions - features that relate E2-BeFx complex to an intermediate of the functional cycle of the Na+,K+-ATPase prior E2P.

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Nissen, P., Fruergaard, m. U., Fedosova, N. U., Andersen, J. L., Shahsavar, A., Quistgaard, E., Poulsen, H., Dach, I.. 2021-11-10. The beryllium fluoride form of the Na+,K+-ATPase and the intermediates of the functional cycle. https://doi.org/10.1101/2021.11.08.467847

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