Fig. 4: The Ca²⁺-binding site of NCLX.

a, Coordination of Ca²⁺ at the Ca²⁺-binding site in the experimental structure (Ca²⁺ shown as a magenta sphere in the zoomed-in view on the right and as a green sphere on the left for contrast). Ca²⁺ is coordinated by the D153 and D471 side-chain oxygens; the N149 and N467 backbone oxygens; and water molecules. b, The density map of the Ca²⁺-binding site of NCLX. The densities are shown as blue meshes (contoured at 14σ), with Ca²⁺ displayed as a magenta sphere and the coordinating water molecules as red spheres. c, Superposition of matrix-facing NCLX in the presence and absence of Ca²⁺. d, Superposition of cytosol-facing NCLX in the presence and absence of Ca²⁺. A magnified view of TM2 and TM9 coordinated by Ca²⁺ is shown on the right.