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. 2013 Jun 17;110(27):10958–10963. doi: 10.1073/pnas.1222308110

Fig. 1.

Fig. 1.

The high-affinity Na+,K+-ATPase E2P–ouabain complex. The E2P–ouabain complex is depicted using the following color codes: red [nucleotide binding (N) domain], blue [phosphorylation (P) domain], light yellow [actuator (A) domain], orange (αM1–2), teal (αM3–4), purple (αM5–6), brown (αM7–10), green (β-subunit), and deep pink (γ-subunit). The CTS binding site is marked CTS. Ouabain is represented by yellow sticks, Mg2+ and the three water molecules by light green and red spheres, respectively. The cholesterol–phospholipid site is marked CLR, with cholesterol and phosphatidylserine depicted in orange and in black sticks, respectively. The carbohydrate moieties are depicted in light pink sticks, confirming the three glycosylation sites at Asn158, Asn193, and Asn265 at the β-subunit. (A) Cartoon representation of the high-affinity Na+,K+-ATPase E2P–ouabain complex. (B) Structural representation of ouabain, illustrating charge relocation in the lactone ring. (C) Well-defined electron density map of the occupied ouabain and cation binding sites. The initial Fo–Fc map obtained after initial rigid body refinement, contoured at 5.0 σ, is depicted in green mesh, and the 2Fo–Fc map, contoured at 1.5 σ, is depicted in gray mesh. (D) Structural alignment of the high-affinity [Mg]E2P–ouabain complex and the low-affinity [K2]E2–MgFx–ouabain complex (11). The [K2]E2–MgFx–ouabain complex in gray cartoon indicates the location of two K+ (dotted spheres). Residues lining ion site II are shown in sticks. (E) Surface representation (hydrophobic moieties in gray, positively charged atoms in blue, negatively charged atoms in red) of the cation and ouabain binding sites of the high-affinity ouabain complex with Mg2+-bound at site II (Left) and the K+-occluded low-affinity ouabain complex (11) (Right), visualized from αM1–2. The map has been intersected along αM4 and αM6. αM4 (depicted in cartoon) subsequently was superimposed onto the figure to demonstrate the spatial rearrangement of the CTS binding site as a consequence of the winding/unwinding of αM4. The interior of the protein is depicted in dark gray.