Model of Rev-erb LBD interactions and heme states. The Rev-erb LBD is schematized as a blue ellipse, the ligand binding pocket as the ligand binding site. White is the unbound site, colored small ellipses are heme-bound, either with the iron in the 3 + oxidation state (red), the 2 + oxidation state (dark blue), or bound by NO in the 2 + oxidation state (light blue). Helix 11 is green and helix 3 is in pink. The corepressor is yellow (β-strand) and orange (α-helix).