title: Spectroscopic investigation of isonitrile complexes of ferric and ferrous microperoxidase 8.
abstract: Microperoxidase 8 (MP8) is able to react with alkyl- and aryl-isonitriles (RNC) both in its reduced and oxidized states, to form MP8Fe(II)- and MP8Fe(III)-CNR complexes. The coordination and spin states of these complexes have been fully characterized by UV-visible and resonance Raman spectroscopies. Both MP8Fe(II)- and MP8Fe(III)-CNR complexes are hexacoordinate low-spin complexes, which bear a single RNC ligand on the distal face of the heme and keep the His 18 ligand on its proximal face, trans to the RNC ligand. A comparison of these characteristics with those of the Fe-CNR complexes of other hemoproteins suggests that both MP8Fe(II)- and MP8Fe(III)-CNR complexes present a Fe-C-N linear arrangement. This may be due to the lack of any interactions of the RNC ligand with the octapeptide of MP8 that is mainly located over the opposite face of the heme. Finally the formation of hexacoordinate low-spin MP8Fe(II)- and MP8Fe(III)-CNR complexes constitutes a new example of the reactivity of MP8 with a new class of weak sigma-donating and strong pi-accepting ligands, which adds to its already very rich coordination chemistry.
authors.affiliation: Laboratoire de Chimie Bioorganique et Bioinorganique, UMR 8124, CNRS, Institut de Chimie Moléculaire et des Matériaux d'Orsay, Bâtiment 420, Université Paris-Sud XI, F-91405 Orsay, France.
authors.forename: Rémy
authors.initials: R
authors.lastname: Ricoux
authors.forename: Sophie
authors.initials: S
authors.lastname: Lecomte
authors.forename: Clotilde
authors.initials: C
authors.lastname: Policar
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Boucher
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Mahy
mesh_terms: D000818:Animals; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism; D005296:Ferrous Compounds / Q000737:chemistry* / Q000378:metabolism; D009570:Nitriles / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry* / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D009570:Nitriles; D010544:Peroxidases; C021799:microperoxidase