A twist on heme signaling.

Proteins in the H-NOX family act as sensors of NO or O2. This family includes soluble guanylate cyclase (sGC), the NO sensor that is responsible for vasodilation and neurotransmission in mammals. The crystal structures of bacterial H-NOX domains have revealed a highly distorted heme cofactor. This distortion has now been shown to be associated with a concerted displacement of the entire N-terminal half of the protein. This displacement likely provides the mechanism for transducing the ligand binding event into signaling.