the rev-erbα protein is structurally unique from other nuclear receptors, in that it lacks helix 12 (h12) in its ligand-binding domain, which is usually responsible for forming the ligand binding pocket in other nuclear receptors. in place of the missing h12, rev-erbα displays a hydrophobic interface that binds the corepressor n-cor, making it a potent transcriptional repressor. all members of the rev-erb family bind heme, which may act as a ligand to regulate their transcriptional activity.