FIG 6.

Interactions affecting ligand binding in ScLDM. (A) PCZ lacks a tertiary hydroxyl and has a water-mediated hydrogen bond network in the SEC. The cartoon and stick representation of carbons for ScLDM6×His is shown in green, with key residues within 4 Å of PCZ in magenta. The carbons in heme are shown in salmon and PCZ in yellow. Waters are shown as small red spheres, and the heme iron is a larger orange sphere. Nitrogens are in blue and oxygens are in red. S507 has been deleted to expose the view into the water-containing pocket. Hydrogen bonds are shown as yellow dashed lines. (B) The VT-1161 tertiary alcohol hydroxyl forms a water-mediated hydrogen bond network involving Y140. The cartoon and stick representation of carbons for ScLDM6×His is shown in green, with key residues within 4 Å of VT-1161 shown in magenta. Heme carbons are in salmon and VT-1161 in yellow. The interaction shown between the H381 imidazole and VT-1161 involves a distance measured as 3.5 Å. (C) The N-1 of the PCZ piperazine group forms a water-mediated hydrogen bond network in the SEC. The net indicates the surface of the SEC. The carbons of amino acids that are within 4 Å of PCZ are shown in magenta, while more distant contributors to the SEC are in cyan. The carbons of PCZ are in yellow. RCC, heme ring C propionate carboxyl. RDC, heme ring D propionate carboxyl.