title: Interactions between substrates and the haem-bound nitric oxide of ferric and ferrous bacterial nitric oxide synthases.
abstract: We report here the resonance Raman spectra of the FeIII-NO and FeII-NO complexes of the bacterial NOSs (nitric oxide synthases) from Staphylococcus aureus and Bacillus subtilis. The haem-NO complexes of these bacterial NOSs displayed Fe-N-O frequencies similar to those of the mammalian NOSs, in presence and absence of L-arginine, indicating that haem-bound NO and L-arginine had similar haem environments in bacterial and mammalian NOSs. The only notable difference between the two types of NOS was the lack of change in Fe-N-O frequencies of the FeIII-NO complexes upon (6R) 5,6,7,8-tetrahydro-L-biopterin binding to bacterial NOSs. We report, for the first time, the characterization of NO complexes with NOHA (N(omega)-hydroxy-L-arginine), the substrate used in the second half of the catalytic cycle of NOSs. In the FeIII-NO complexes, both L-arginine and NOHA induced the Fe-N-O bending mode at nearly the same frequency as a result of a steric interaction between the substrates and the haem-bound NO. However, in the FeII-NO complexes, the Fe-N-O bending mode was not observed and the nu(Fe-NO) mode displayed a 5 cm(-1) higher frequency in the complex with NOHA than in the complex with L-arginine as a result of direct interactions that probably involve hydrogen bonds. The different behaviour of the substrates in the FeII-NO complexes thus reveal that the interactions between haem-bound NO and the substrates are finely tuned by the geometry of the Fe-ligand structure and are relevant to the use of the FeII-NO complex as a model of the oxygenated complex of NOSs.
authors.affiliation: Département de Biochimie et de Microbiologie, and Centre de Recherche sur la fonction, la structure et l'ingénierie des protéines (CREFSIP), Université Laval, Québec, Canada.
authors.forename: François J M
authors.initials: FJ
authors.lastname: Chartier
authors.forename: Manon
authors.initials: M
authors.lastname: Couture
mesh_terms: D000818:Animals; D001120:Arginine / Q000378:metabolism*; D001412:Bacillus subtilis / Q000201:enzymology*; D001426:Bacterial Proteins / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D005290:Ferric Compounds / Q000378:metabolism*; D005296:Ferrous Compounds / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D007700:Kinetics; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013059:Spectrum Analysis, Raman; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D005290:Ferric Compounds; D005296:Ferrous Compounds; D011994:Recombinant Proteins; D006418:Heme; D001120:Arginine; D019001:Nitric Oxide Synthase