Mutations in the FMN domain modulate MCD spectra of the heme site in the oxygenase domain of inducible nitric oxide synthase.
The nitric oxide synthase (NOS) output state for NO production is a complex of the flavin mononucleotide (FMN)-binding domain and the heme domain, and thereby it facilitates the interdomain electron transfer from the FMN to the catalytic heme site. Emerging evidence suggests that interdomain FMN-heme interactions are important in the formation of the output state because they guide the docking of the FMN domain to the heme domain. In this study, notable effects of mutations in the adjacent FMN domain on the heme structure in a human iNOS bidomain oxygenase/FMN construct have been observed by using low-temperature magnetic circular dichroism (MCD) spectroscopy. The comparative MCD study of wild-type and mutant proteins clearly indicates that a properly docked FMN domain contributes to the observed L-Arg perturbation of the heme MCD spectrum in the wild-type protein and that the conserved surface residues in the FMN domain (E546 and E603) play key roles in facilitating a productive alignment of the FMN and heme domains in iNOS.
Sempombe
Joseph
J
Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
Elmore
Bradley O
BO
Sun
Xi
X
Dupont
Andrea
A
Ghosh
Dipak K
DK
Guillemette
J Guy
JG
Kirk
Martin L
ML
Feng
Changjian
C
D001665:Binding Sites; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D005486:Flavin Mononucleotide / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006418:Heme / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009154:Mutation; D052247:Nitric Oxide Synthase Type II / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary
D006418:Heme; D005486:Flavin Mononucleotide; D052247:Nitric Oxide Synthase Type II