Electron nuclear double resonance (ENDOR) from heme and histidine nitrogens in single crystals of aquometmyoglobin

Scholes, Charles P.; Lapidot, Aviva; Mascarenhas, Rita; Inubushi, Toshiro; Isaacson, R. A.; Fehér, G.

doi:10.1021/ja00374a007

Cited by 111 publications

(213 citation statements)

References 2 publications

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“…Figure 6f shows the simulated HYSCORE spectra, for which the hyperfine and nuclear-quadrupole parameters from table 2 were used. The hyperfine couplings of both the heme and histidine nitrogens are positive, as was previously observed for other high spin compounds [37].…”

Section: Continuous-wave Electron Paramagnetic Resonance (Cw Epr) Cwsupporting

confidence: 85%

Probing the heme-pocket structure of the paramagnetic forms of cytoglobin and a distal histidine mutant using electron paramagnetic resonance

et al. 2007

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Section: Continuous-wave Electron Paramagnetic Resonance (Cw Epr) Cwsupporting

confidence: 85%

Probing the heme-pocket structure of the paramagnetic forms of cytoglobin and a distal histidine mutant using electron paramagnetic resonance

et al. 2007

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“…, 41 we also found that deviation from first-order resonance frequencies is less than ∼0.2 MHz. Spectrum (A) was simulated with five 14 N nuclei and a slight inequivalency of the porphyrin hfcs (A z = 7.9 and 8.1 MHz respectively), which causes the observed broadening.…”

supporting

confidence: 67%

“…The intensity and the sharpness of the spectra in this region are very consistent with spectra previously reported for magnetically equivalent porphyrin nitrogens. 41 The comparison with the reference spectra (B, C) and the simulations support this assignment.…”

mentioning

confidence: 53%

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Multifrequency Electron Paramagnetic Resonance Characterization of PpoA, a CYP450 Fusion Protein that Catalyzes Fatty Acid Dioxygenation

et al. 2011

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PpoA is a fungal dioxygenase that produces hydroxylated fatty acids involved in the regulation of the life cycle and secondary metabolism of Aspergillus nidulans. It was recently proposed that this novel enzyme employs two different heme domains to catalyze two separate reactions: within a heme peroxidase domain, linoleic acid is oxidized to (8R)-hydroperoxyoctadecadienoic acid [(8R)-HPODE]; in the second reaction step (8R)-HPODE is isomerized within a P450 heme thiolate domain to 5,8-dihydroxyoctadecadienoic acid. In the present study, pulsed EPR methods were applied to find spectroscopic evidence for the reaction mechanism, thought to involve paramagnetic intermediates. We observe EPR resonances of two distinct heme centers with g-values typical for Fe(III) S = 5/2 high-spin (HS) and Fe(III) S = 1/2 low-spin (LS) hemes. 14N ENDOR spectroscopy on the S = 5/2 signal reveals resonances consistent with an axial histidine ligation. Reaction of PpoA with the substrate leads to the formation of an amino acid radical on the early millisecond time scale concomitant to a substantial reduction of the S = 5/2 heme signal. High-frequency EPR (95- and 180-GHz) unambiguously identifies the new radical as a tyrosyl, based on g-values and hyperfine couplings from spectral simulations. The radical displays enhanced T 1-spin–lattice relaxation due to the proximity of the heme centers. Further, EPR distance measurements revealed that the radical is distributed among the monomeric subunits of the tetrameric enzyme at a distance of approximately 5 nm. The identification of three active paramagnetic centers involved in the reaction of PpoA supports the previously proposed reaction mechanism based on radical chemistry.

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“…To avoid this problem, we prepared mixed crystals of myoglobin in which the majority of the molecules (90%) were in the diamagnetic CO-ligated form. In these crystals, we observed and analyzed in detail the ENDOR signals at different orientations of the crystal with respect to the magnetic field (141).…”

Section: The Electronic Structure Of Hemesmentioning

confidence: 99%

My Road to Biophysics: Picking Flowers on the Way to Photosynthesis

Fehér

2002

Annu. Rev. Biophys. Biomol. Struct.

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Electron nuclear double resonance (ENDOR) from heme and histidine nitrogens in single crystals of aquometmyoglobin

Cited by 111 publications

References 2 publications

Probing the heme-pocket structure of the paramagnetic forms of cytoglobin and a distal histidine mutant using electron paramagnetic resonance

Probing the heme-pocket structure of the paramagnetic forms of cytoglobin and a distal histidine mutant using electron paramagnetic resonance

Multifrequency Electron Paramagnetic Resonance Characterization of PpoA, a CYP450 Fusion Protein that Catalyzes Fatty Acid Dioxygenation

My Road to Biophysics: Picking Flowers on the Way to Photosynthesis

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