Cyanide replaces substrate in obligate-ordered addition of nitric oxide to the non-heme mononuclear iron AvMDO active site

Improved resolution of 3-mercaptopropionate dioxygenase active site provided by ENDOR spectroscopy offers insight into catalytic mechanism

“…Also observed is an iron-coordinated chloride trans to His90 which interacts with the hydroxyl group of Tyr159 to form an ion-dipole interaction. This represents the putative dioxygen binding site and is designated the axial Fe-position to differentiate it from the equatorial substrate-binding sites ( 27 , 39 , 40 ). 3HPA differs from the native substrate by substitution of a single O-atom (hydroxyl versus thiol), and thus it is reasonable to assume an equivalent bidentate coordination of the native 3MPA substrate.…”