1cmj
|
CRYSTAL STRUCTURES OF FERRIC-NO COMPLEXES OF FUNGAL NITRIC OXIDE REDUCTASE AND THEIR SER286 MUTANTS AT CRYOGENIC TEMPERATURE
OverviewOverview
Fungal nitric-oxide reductase (NOR) is a heme enzyme that catalyzes the, reduction of NO to N(2)O through its ferric-NO complex, the first, intermediate of the catalysis. Crystal structures of the ferric-NO forms, of wild type (WT) fungal NOR, and of the Ser(286) --> Val and Ser(286) -->, Thr mutant enzymes were determined to 1.7-A resolution at cryogenic, temperature (100 K). This shows a slightly tilted and bent NO binding to, the heme iron, in sharp contrast to the highly bent NO coordination found, in ferrous hemoproteins. In the WT structure, a specific hydrogen-bonding, network that connects the active site to the solvent was identified, H(2)O(Wat(74))-Ser(286)-H(2)O(Wat(33))-Asp(393)-solvent. Wat(74) is, located 3.10 A from the iron-bound NO. Replacement of Ser(286) with Val or, Thr scarcely alters the NO coordination structure but expels the water, molecules, Wat(74) from the active site. The Asp(393) mutation does not, influence the position of Wat(74), but disrupts the hydrogen-bonding, network at Wat(33), as evidenced by enzymatic, kinetic, and spectroscopic, (resonance Raman and IR) results. The structural changes observed upon the, Ser(286) or the Asp(393) mutation are consistent with the dramatic loss of, the enzymatic activity for the NO reduction of fungal NOR. We have, conclusively identified the water molecule, Wat(74), adjacent to the, iron-bound NO as a proton donor to the Fe-NO moiety. In addition, we find, the hydrogen-bonding network, H(2)O(Wat(74))-Ser(286)-H(2)O(Wat(33))-Asp(393), as a proton delivery, pathway in the NO reduction reaction by fungal NOR.
About this StructureAbout this Structure
1CMJ is a Single protein structure of sequence from Fusarium oxysporum with HEM and NO as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Proton delivery in NO reduction by fungal nitric-oxide reductase. Cryogenic crystallography, spectroscopy, and kinetics of ferric-NO complexes of wild-type and mutant enzymes., Shimizu H, Obayashi E, Gomi Y, Arakawa H, Park SY, Nakamura H, Adachi S, Shoun H, Shiro Y, J Biol Chem. 2000 Feb 18;275(7):4816-26. PMID:10671516
Page seeded by OCA on Tue Nov 20 12:34:57 2007