title: Reaction of human myoglobin and nitric oxide. Heme iron or protein sulfhydryl (s) nitrosation dependence on the absence or presence of oxygen.
abstract: The amino acid sequence of human myoglobin (Mb) is similar to other mammalian Mb except for a unique cysteine residue at position 110 (Cys(110)). Anaerobic treatment of ferrous forms of wild-type human Mb, the C110A variant of human Mb or horse heart Mb, with either authentic NO or chemically derived NO in vitro yields heme-NO complexes as detected by electron paramagnetic resonance spectroscopy (EPR). By contrast, no EPR-detectable heme-NO complex was observed from the aerobic reactions of NO and either the ferric or oxy-Mb forms of wild-type human or horse heart myoglobins. Mass analyses of wild-type human Mb treated aerobically with NO indicated a mass increase of approximately 30 atomic mass units (i.e., NO/Mb = 1 mol/mol). Mass analyses of the corresponding apoprotein after heme removal showed that NO was associated with the apoprotein fraction. New electronic maxima were detected at A(333 nm) (epsilon = 3665 +/- 90 mol(-)(1) cm(-)(1); mean +/- S.D.) and A(545 nm) (epsilon = 44 +/- 3 mol(-)(1) cm(-)(1)) in solutions of S-nitrosated wild-type human Mb (similar to S-nitrosoglutathione). Importantly, the sulfhydryl S-H stretch vibration for Cys(110) measured by Fourier transform infrared (nu approximately 2552 cm(-)(1)) was absent for both holo- and apo- forms of the wild-type human protein after aerobic treatment of the protein with NO. Together, these data indicate that the reaction of wild-type human Mb and NO yields either heme-NO or a novel S-nitrosated protein dependent on the oxidation state of the heme iron and the presence or absence of dioxygen.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3.
authors.forename: P K
authors.initials: PK
authors.lastname: Witting
authors.forename: D J
authors.initials: DJ
authors.lastname: Douglas
authors.forename: A G
authors.initials: AG
authors.lastname: Mauk
mesh_terms: D000818:Animals; D006801:Humans; D009211:Myoglobin / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D009603:Nitroso Compounds / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D013057:Spectrum Analysis; D013438:Sulfhydryl Compounds / Q000378:metabolism*
chemical_list: D009211:Myoglobin; D009603:Nitroso Compounds; D013438:Sulfhydryl Compounds; D009569:Nitric Oxide; D010100:Oxygen