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. 2018 Jul 20;7:e39775. doi: 10.7554/eLife.39775

Figure 7. Ligand density in non-symmetrized SthK maps.

Figure 7.

Full-length, non-symmetrized C1 density maps for apo (A), cAMP-bound (B), and cGMP-bound (C) SthK. Overall protein density is in grey surface, cAMP density is in magenta (B), and cGMP density is in cyan (C). cAMP (D) and cGMP (E) density for each binding site in the four subunits of the tetramer, contoured at 6 σ (grey mesh), 11 σ (orange mesh), and 15 σ (dark blue mesh). All four ligand densities (for cAMP and cGMP) decrease at the same rate as the contour levels increase, and disappear at ~15 σ, and at the same rate as the protein density in a nearby region (rightmost panels in D, E), suggesting that all binding sites are occupied with ligand and the occupancy is close to 1 in each of the sites. Ligands and protein are drawn in stick representation.