Myoglobin Catalyzes Its Own Nitration

Bourassa, James; Ives, Elizabeth P.; Marqueling, Ann L.; Shimanovich, Roman; Groves, John T.

doi:10.1021/ja015621m

Cited by 89 publications

(128 citation statements)

References 28 publications

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“…Recombination of the ⅐ NO 2 radical with ferrylHb within the heme cavity would mainly yield metHb and NO 3 Ϫ (Equation 10), whereas a small fraction of the radicals could diffuse out (Equation 11) and yield ⅐ NO 2 and ferrylHb. Ferric iron could act as a Lewis acid and catalyze the isomerization of peroxynitrite to nitrate (4,54) as has been already reported for iron(III) porphyrins and metmyoglobin (14,15). A similar transient metHb-peroxynitrite complex was detected during the ⅐ NO-mediated oxidation of oxyHb, which rapidly evolves to metHb and nitrate (12).…”

Section: Discussionsupporting

confidence: 59%

“…considered that involve the formation of intermediate hemoglobin-NO x complexes, such as those observed during the oxidation of oxyHb by ⅐ NO (12) and probably by ⅐ NO 2 and/or NO 2 Ϫ (13). Indeed, in the oxyHb-mediated oxidation of ⅐ NO, a transient metHb-peroxynitrite complex is detected that rapidly evolves to metHb and nitrate (12 A similar complex was also proposed for the isomerization of peroxynitrite catalyzed by metmyoglobin or iron-porphyrins (14,15).…”

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confidence: 81%

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Reaction of Human Hemoglobin with Peroxynitrite

Romero

Radí

Linares

et al. 2003

Journal of Biological Chemistry

119

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Peroxynitrite, a strong oxidant formed intravascularly in vivo, can diffuse onto erythrocytes and be largely consumed via a fast reaction (2 ؋ 10 4 M ؊1 s ؊1 ) with oxyhemoglobin. The reaction mechanism of peroxynitrite with oxyhemoglobin that results in the formation of methemoglobin remains to be elucidated. In this work, we studied the reaction under biologically relevant conditions using millimolar oxyhemoglobin concentrations and a stoichiometric excess of oxyhemoglobin over peroxynitrite. The results support a reaction mechanism that involves the net one-electron oxidation of the ferrous heme, isomerization of peroxynitrite to nitrate, and production of superoxide radical and hydrogen peroxide. Homolytic cleavage of peroxynitrite within the heme iron allows the formation of ferrylhemoglobin in ϳ10% yields, which can decay to methemoglobin at the expense of reducing equivalents of the globin moiety. Indeed, spin-trapping studies using 2-methyl-2-nitroso propane and 5,5 dimethyl-1-pyrroline-N-oxide (DMPO) demonstrated the formation of tyrosyl-and cysteinyl-derived radicals. DMPO also inhibited covalently linked dimerization products and led to the formation of DMPO-hemoglobin adducts. Hemoglobin nitration was not observed unless an excess of peroxynitrite over oxyhemoglobin was used, in agreement with a marginal formation of nitrogen dioxide. The results obtained support a role of oxyhemoglobin as a relevant intravascular sink of peroxynitrite.Peroxynitrite, 1 a strong oxidant formed intravascularly in vivo by the diffusion-limited reaction between nitric oxide ( ⅐ NO) and superoxide (O 2 . ) radicals (1-5), rapidly oxidizes human oxyhemoglobin (oxyHb) 2 (k 2 ϭ 2 ϫ 10 4 M Ϫ1 s Ϫ1 at 37°C and pH 7.4 (6,7)) to yield methemoglobin (metHb) as the final product. Peroxynitrite can behave as either a one-or two-electron oxidant during its direct reaction with transition metal centers; therefore, it is not apparent how metHb is formed. Recently, an initial two-electron oxidation process has been proposed leading to the formation of a high oxidation state intermediate, ferrylhemoglobin (ferrylHb) (8, 9). However, the ferrylHb intermediate detected during reaction of oxyHb with peroxynitrite has a very short half-life (i.e. milliseconds), and it can only be clearly observed when trapped with sodium sulfide (8, 9). Even under excess of sodium sulfide, the yields of sulfo-hemoglobin obtained were low (ϳ 10 -15% of metHb yield). This contrasts with the two-electron oxidation product obtained with oxyHb under excess of hydrogen peroxide (H 2 O 2 ), which yields a relatively stable ferrylHb intermediate (i.e. minutes) that can be observed directly by spectrophotometric techniques (10). If peroxynitrite oxidizes oxyHb by a two-electron oxidation process, nitrite and molecular oxygen should be produced in addition to ferrylHb (Equation 1):Neither nitrite nor molecular oxygen yields have been assessed yet, so the mechanism proposed in Equation 1 cannot be confirmed with the available data. Other authors have previously prop...

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Section: Discussionsupporting

confidence: 59%

mentioning

confidence: 81%

Reaction of Human Hemoglobin with Peroxynitrite

Romero

Radí

Linares

et al. 2003

Journal of Biological Chemistry

119

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“…It turns out, however, that Mb is actually allosteric and has at least two functions (25,26). The allostery is explained through the hierarchical organization of the energy landscape.…”

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confidence: 99%

Myoglobin: The hydrogen atom of biology and a paradigm of complexity

Frauenfelder

McMahon²,

Fenimore³

2003

Proc. Natl. Acad. Sci. U.S.A.

199

156

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“…This result may also explain why the conserved cysteine in the active center of TrpRS I has been changed to a hydrophobic residue in TrpRS II. It has been well demonstrated in myoglobin and peroxidases that heme proteins catalyze nitration of their aromatic residues when nitric oxide or other oxidized nitrogen species are available (33)(34)(35)(36)(37).…”

Section: Discussionmentioning

confidence: 99%

An unusual tryptophanyl tRNA synthetase interacts with nitric oxide synthase in Deinococcus radiodurans

Buddha

Keery

Crane

2004

Proc. Natl. Acad. Sci. U.S.A.

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In mammals, nitric oxide synthases (NOSs) produce nitric oxide for signaling and defense functions; in Streptomyces, NOS proteins nitrate a tryptophanyl moiety in synthesis of a phytotoxin. We have discovered that the NOS protein from the radiation-resistant bacterium Deinococcus radiodurans (deiNOS) associates with an unusual tryptophanyl tRNA synthetase (TrpRS). D. radiodurans contains genes for two TrpRSs: the first has Ϸ40% sequence identity to typical TrpRSs, whereas the second, identified as the NOS-interacting protein (TrpRS II), has only Ϸ29% identity. TrpRS II is induced after radiation damage and contains an N-terminal extension similar to those of proteins involved in stress responses. N itric oxide synthases (NOSs) are highly regulated enzymes that synthesize the potent cytotoxin and signal molecule nitric oxide (NO) from L-arginine (L-arg) (1-3). In mammals, NOSs are responsible for many functions that range from protection against pathogens and tumor cells to blood pressure regulation and nerve transmission. Bacterial NOS proteins also catalyze the hemedependent conversion of L-arg to NO in vitro (4-7); however, in at least one case, they have been shown to function in the nitration of secondary metabolites (8). Mammalian NOSs are homodimers that contain an N-terminal heme oxygenase domain and a C-terminal flavoprotein reductase domain. The catalytic oxygenase domain binds L-arg, heme and the redox-active cofactor 6R-tetrahydrobiopterin, whereas the electron-supplying reductase domain binds FAD, FMN, and NADPH.Bacterial NOSs from Deinococcus radiodurans (deiNOS), Staphylococcus aureus (saNOS), and Bacillus subtilis (bsNOS) are homologous to the mammalian N-terminal heme oxygenase domain but lack an associated C-terminal flavoprotein reductase domain and N-terminal regions that bind Zn 2ϩ , the dihydroxypropyl side chain of 6R-tetrahydrobiopterin, and the adjacent subunit of the dimer (4, 6, 9). Nevertheless, deiNOS, bsNOS, and saNOS are dimeric, have a normal heme environment, bind substrate L-arg, and produce nitrogen oxide species in a manner dependent on pterin (either with 6R-tetrahydrobiopterin or with the related cofactor tetrahydrofolate (4, 5, 7). Conservation of key residues among bacterial and mammalian NOSs also suggests that all bacterial NOSs produce nitrogen oxides from L-arg and the NOS intermediate N -hydroxy-L-arginine (NHA) (6, 9). bsNOS has been directly shown to produce nitric oxide (5).The first biological function for a bacterial NOS was determined for Streptomyces (8). Pathogenic Streptomyces species (Streptomyces scabies, Streptomyces acidiscabies, Streptomyces turgidiscabies, and Streptomyces ipomoea) produce a family of unusual nitrated cyclic dipeptides [derivatives of cyclo-(L-tryptophanyl-L-phenylalanyl)], called thaxtomins (10), that contain a 4-nitro-tryptophanyl moiety and interfere with the formation of plant cell walls (11). A large pathogenicity island that contains the nonribosomal peptide synthase genes responsible for production of the thaxtomin dipeptide also ...

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Myoglobin Catalyzes Its Own Nitration

Cited by 89 publications

References 28 publications

Reaction of Human Hemoglobin with Peroxynitrite

Reaction of Human Hemoglobin with Peroxynitrite

Myoglobin: The hydrogen atom of biology and a paradigm of complexity

An unusual tryptophanyl tRNA synthetase interacts with nitric oxide synthase in Deinococcus radiodurans

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