Biology subjects

Fedosova, N. U.

Publications and source records attributed to Fedosova, N. U..

2 recordsLinked to original sources

bioRxiv2021

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

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.

biochemistry↗

bioRxiv2020

Beneficent and maleficent effects of cations on bufadienolide binding to Na+,K+-ATPase

Kinetic properties and crystal structures of the Na+,K+-ATPase in complex with cardiotonic steroids (CTS) revealed significant differences between CTS subfamilies (Laursen et al., 2015): beneficial effects of K+ on bufadienolide binding strongly contrasted with K+/cardenolide antagonism. To solve this riddle we applied docking and molecular dynamics simulations of the complexes involving Na+,K+-ATPase, bufadienolides (bufalin, cinobufagin), and ions (K+, Na+, Mg2+). The results revealed that bufadienolide binding is affected by i) electrostatic attraction of the lactone ring by a cation, and ii) the ability of a cation to stabilize and "shape" the site constituted by transmembrane helices of the -subunit (M1-6). The latter effect was due to varying coordination patterns involving amino acid residues from helix bundles M1-4 and M5-10. Substituents on the steroid core of a bufadienolide add to and modify the cation effects. The above rationale is fully consistent with the ion effects on the kinetics of Na+,K+-ATPase/bufadienolide interactions.

biophysics↗