Fig. 3.

Proximal-bound, five-coordinate NO complex and NO-induced heme flattening. (A) Zoomed-in view of the Fe^II-NO So H-NOX heme pocket shows NO bound in a bent geometry to the proximal heme face, with the heme-ligating histidine (residue 103) considerably displaced from the heme iron. The 2mF_o-DF_c electron density (1σ) is displayed in blue mesh. (B) Alignment of the Fe^II and Fe^II-NO hemes (aligned using pyrroles B and C; molecules A of the ASU) shows an increase in heme planarity upon histidine dissociation.