An interpretation of the three line EPR spectrum of nitric oxide hemeproteins and related model systems:

Kon, Hideo

doi:10.1016/0005-2795(75)90012-4

Cited by 84 publications

(25 citation statements)

References 22 publications

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“…2 compares the EPR spectrum of the 15 NO-bound ferrous heme-⌬H45A complex to that of the wild-type complex. The spectral shape of the ⌬H45A mutant complex is typical of a five coordinate 15 NO heme species (30), and the spectrum of the wild-type complex is 6 coordinate with an imidazole axial ligand as reported for the 28-kDa tryptic HO-2 fragment (18). This infers that, in the ⌬H45A NO complex, the fifth coordination of the heme iron is vacant.…”

Section: Properties Of Truncated Soluble Ho-2-supporting

confidence: 61%

Identification of Histidine 45 as the Axial Heme Iron Ligand of Heme Oxygenase-2

Ishikawa¹,

Matera²,

Zhou³

et al. 1998

Journal of Biological Chemistry

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A truncated, soluble, and enzymatically active form of human heme oxygenase-2 (⌬HHO2) was expressed in Escherichia coli. To identify the axial heme ligand of HO-2, His-45 to Ala (⌬H45A) and His-152 to Ala (⌬H152A) mutants have been prepared using this expression system. ⌬H45A could form a 1:1 complex with hemin but was completely devoid of the heme degradation activity. A 5-coordinate-type ferrous NO EPR spectrum was observed for the heme-⌬H45A complex. The ⌬H152A mutant was expressed as an inclusion body and was recovered from the lysis pellet by dissolution in urea followed by dialysis. The solubilized fraction obtained, however, was composed of a mixture of a functional enzyme and an inactive fraction. The inactive fraction was removed by Sephadex G-75 column chromatography since it eluted out of the column at the void volume. The gel filtration-purified ⌬H152A exhibited spectroscopic and enzymatic properties identical to those of wild-type. We conclude, in contrast to the previous reports

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Section: Properties Of Truncated Soluble Ho-2-supporting

confidence: 61%

Identification of Histidine 45 as the Axial Heme Iron Ligand of Heme Oxygenase-2

Ishikawa¹,

Matera²,

Zhou³

et al. 1998

Journal of Biological Chemistry

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“…The EPR spectrum of the ferrous microsomal cytochrome P-450-NO complex changes with time to that of the ferrous P-420-NO complex also shown in fig.3. The EPR spectrum of the P-420--NO complex resemblesthat of sodium dodecyl sulfatemodified hemoglobin [ 1 ] and, as has been proposed for the NO derivatives of structurally perturbed Fe(II) hemeproteins [5,6], may indicate that the bond to the axial ligand trans to the bound NO is severely distorted or broken. The EPR spectra previously reported for the ferrous-NO complex of cytochrome P-450 in microsomes [11,12] and in submicrosomal particles [9,10] resemble that of the ferrous P-420-NO complex and support the above suggestion that the ferrous microsomal cytochrome P-450-NO complex is unstable.…”

Section: Resultsmentioning

confidence: 99%

“…For example, it has been demonstrated that hemoglobin and myoglobin form ferrous NO complexes which exhibit EPR spectra having superhyperfine lines in the gz signal, consistent with electron spin-nuclear spin interaction of the unpaired electron of the bound NO with a trans axial ligand, presumably due to one of the 14N atoms of an imidazole moiety [1][2][3][4]. Perturbation of the protein structure either by a denaturing agent [1,5] or an allosteric effector [6] appears to result in either distortion or complete breakage of the bond between the heine iron and the trans ligand resulting in a pentacoordinate heine-NO species which has a sharp 3-line gz EPR signal. Other hemeproteins, including horseradish peroxidase (HRP) and cytochrome c peroxidase (CCP), form stable ferric, as well as ferrous, NO complexes [7].…”

Section: Introductionmentioning

confidence: 99%

Nitric oxide complexes of cytochrome P‐450

Ebel¹,

O'Keeffe²,

Peterson³

1975

FEBS Letters

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“…The nitric oxide gas was further purified by the method of Kon. 12 A nitric oxide stock solution was prepared each day immediately before the experiment as follows: Artificial CSF was bubbled with 100% nitrogen in a gas-tight container for 10 minutes. Nitric oxide was then introduced at 10 psi for 1 minute.…”

Section: Methodsmentioning

confidence: 99%

H2O2 and endothelium-dependent cerebral arteriolar dilation. Implications for the identity of endothelium-derived relaxing factor generated by acetylcholine.

1990

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We studied the mechanism of the vasodilator effect of H2O2 on cerebral arterioles and its effect on endothelium-dependent responses to acetylcholine. Topical application of H2O2 (0.1-1 microM) on the brain surface of anesthetized cats equipped with cranial windows induced dose-dependent arteriolar dilation, which was markedly inhibited by topical deferoxamine, showing that it was probably mediated by generation of hydroxyl radical. Higher concentrations of H2O2 (3 microM) also induced dilation, which was unaffected by deferoxamine, indicating the participation of other mechanisms. After topical application of H2O2, endothelium-dependent responses to acetylcholine were eliminated or converted to vasoconstriction, and in bioassay experiments, acetylcholine-mediated endothelium-derived relaxing factor (EDRF) was absent. Superoxide dismutase plus catalase restored the appearance of transferable EDRF after 1 microM H2O2 but not after 3 microM H2O2. Application of H2O2 in the assay window eliminated the responses to nitroprusside and nitric oxide but did not affect responses to adenosine, to EDRF from the donor window, or responses to S-nitroso-L-cysteine. The inhibiting effect of H2O2 on the response to nitroprusside was partially eliminated after topical application of N-acetyl-L-cysteine. The results show that H2O2 inhibits the vasodilator action of nitroprusside and nitric oxide probably because it oxidizes thiols in vascular smooth muscle and prevents the formation of a nitrosothiol. EDRF from acetylcholine and S-nitroso-L-cysteine still produce dilation in the presence of the blockade induced by H2O2. The findings suggest strongly that the EDRF from acetylcholine in cerebral vessels is a nitrosothiol like S-nitroso-L-cysteine.

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An interpretation of the three line EPR spectrum of nitric oxide hemeproteins and related model systems:

Cited by 84 publications

References 22 publications

Identification of Histidine 45 as the Axial Heme Iron Ligand of Heme Oxygenase-2

Identification of Histidine 45 as the Axial Heme Iron Ligand of Heme Oxygenase-2

Nitric oxide complexes of cytochrome P‐450

H2O2 and endothelium-dependent cerebral arteriolar dilation. Implications for the identity of endothelium-derived relaxing factor generated by acetylcholine.

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