Extended Data Fig. 5: EM maps of CATSPER1–4.

a, Electron density maps of each segment of the transmembrane helices of CATSPER1–4. The boundaries of each displayed segment are labelled. The densities, shown as blue meshes, are contoured at 3–4σ in PyMOL. b, Electron density map of the selectivity filter and the pore helices. The densities are contoured at 4σ. Two tentatively assigned Na⁺ ions are shown as purple spheres. c, Electron density maps of detergent-like molecules. These densities may also belong to cholesterol or steroid hormones under physiological conditions. Three GDN molecules are tentatively assigned to these densities. The densities are found in a semi-open cavity formed by the S3, S4 and S4–5 segments of CATSPER1, but not CATSPER2–4, whose corresponding cavities are smaller. d, Structural superimposition of CATSPER1–4 indicates that CATSPER1 has a larger cavity for binding of detergent-like molecules.