title: Mutation in the flavin mononucleotide domain modulates magnetic circular dichroism spectra of the iNOS ferric cyano complex in a substrate-specific manner.
abstract: We have obtained low-temperature magnetic circular dichroism (MCD) spectra for ferric cyano complexes of the wild type and E546N mutant of a human inducible nitric oxide synthase (iNOS) oxygenase/flavin mononucleotide (oxyFMN) construct. The mutation at the FMN domain has previously been shown to modulate the MCD spectra of the l-arginine-bound ferric iNOS heme (Sempombe, J.; et al. J. Am. Chem. Soc. 2009, 131, 6940-6941). The addition of l-arginine to the wild-type protein causes notable changes in the CN(-)-adduct MCD spectrum, while the E546N mutant spectrum is not perturbed. Moreover, the MCD spectral perturbation observed with l-arginine is absent in the CN(-) complexes incubated with N-hydroxy-L-arginine, which is the substrate for the second step of NOS catalysis. These results indicate that interdomain FMN-heme interactions exert a long-range effect on key heme axial ligand-substrate interactions that determine substrate oxidation pathways of NOS.
authors: Department of Chemistry and Chemical Biology, The University of New Mexico, New Mexico 87131, USA.
authors: Joseph
authors: J
authors: Sempombe
authors: Mary Grace I
authors: MG
authors: Galinato
authors: Bradley O
authors: BO
authors: Elmore
authors: Weihong
authors: W
authors: Fan
authors: J Guy
authors: JG
authors: Guillemette
authors: Nicolai
authors: N
authors: Lehnert
authors: Martin L
authors: ML
authors: Kirk
authors: Changjian
authors: C
authors: Feng
mesh_terms: D002942:Circular Dichroism; D005290:Ferric Compounds / Q000378:metabolism*; D005486:Flavin Mononucleotide; D006801:Humans; D008280:Magnetics; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D052247:Nitric Oxide Synthase Type II / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity
chemical_list: D005290:Ferric Compounds; D050505:Mutant Proteins; D005486:Flavin Mononucleotide; D052247:Nitric Oxide Synthase Type II