Axial ligation modes in iron(III) porphyrins. Models for the oxidized reaction states of cytochrome P-450 enzymes and the molecular structure of iron(III) protoporphyrin IX dimethyl ester p-nitrobenzenethiolate

Tang, S. C.; Koch, Stephen A.; Papaefthymiou, Georgia C.; Foner, S.; Frankel, Richard B.; Ibers, James A.; Holm, R. H.

doi:10.1021/ja00425a008

Cited by 216 publications

(87 citation statements)

References 10 publications

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“…The same situation was observed in a small molecule analogue, the para-nitrothiophenol thiolate complex of ferric protoporphyrin IX (FePSNP), reported by Tang et al (34). In P450-CAM, the S γ atom of the proximal cysteine is somewhat displaced off from the heme center and the S γ -Fe 3+ bonds form angles of 83° and 82° (in the two molecules of the unit cell) to the porphyrin plane.…”

Section: Structure Of Ferric H93g·bme Mb and Comparison With Cytochrosupporting

confidence: 70%

Structures of Thiolate- and Carboxylate-Ligated Ferric H93G Myoglobin: Models for Cytochrome P450 and for Oxyanion-Bound Heme Proteins^,

et al. 2006

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Crystal structures of the ferric H93G myoglobin (Mb) cavity mutant containing either an anionic proximal thiolate sulfur donor or a carboxylate oxygen donor ligand are reported at 1.7 and 1.4 A resolution, respectively. The crystal structure and magnetic circular dichroism spectra of the H93G Mb beta-mercaptoethanol (BME) thiolate adduct reveal a high-spin, five-coordinate complex. Furthermore, the bound BME appears to have an intramolecular hydrogen bond involving the alcohol proton and the ligated thiolate sulfur, mimicking one of the three proximal N-H...S hydrogen bonds in cytochrome P450. The Fe is displaced from the porphyrin plane by 0.5 A and forms a 2.41 A Fe-S bond. The Fe(3+)-S-C angle is 111 degrees , indicative of a covalent Fe-S bond with sp(3)-hybridized sulfur. Therefore, the H93G Mb.BME complex provides an excellent protein-derived structural model for high-spin ferric P450. In particular, the Fe-S bond in high-spin ferric P450-CAM has essentially the same geometry despite the constraints imposed by covalent linkage of the cysteine to the protein backbone. This suggests that evolution led to the geometric optimization of the proximal Fe-S(cysteinate) bond in P450. The crystal structure and spectral properties of the H93G Mb acetate adduct reveal a high-spin, six-coordinate complex with proximal acetate and distal water axial ligands. The distal His-64 forms a hydrogen bond with the bound water. The Fe-acetate bonding geometry is inconsistent with an electron pair along the Fe-O bond as the Fe-O-C angle is 152 degrees and the Fe is far from the plane of the acetate. Thus, the Fe-O bonding is ionic. The H93G Mb cavity mutant has already been shown to be a versatile model system for the study of ligand binding to heme proteins; this investigation affords the first structural evidence that nonimidazole exogenous ligands bind in the proximal ligation site.

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Section: Structure Of Ferric H93g·bme Mb and Comparison With Cytochrosupporting

confidence: 70%

Structures of Thiolate- and Carboxylate-Ligated Ferric H93G Myoglobin: Models for Cytochrome P450 and for Oxyanion-Bound Heme Proteins^,

et al. 2006

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“…While the complex was high-spin at room temperature, the EPR evidence indicates that the complex shifts to a low-spin complex in the frozen state at 77 K. In DMF, the complex shifts completely to the lowspin complex with g-values of 2.41, 2.27 and 1.93, which is similar to the g-values of other ferric porphyrins with thiolate ligands (Fe(OEP)(SPh)(DMF): 2.42, 2.27 and 1.92 [43]). The intensity of the high-spin EPR signal decreased linearly with the concentration of thiosulfate, reaching zero intensity with a 1:1 ferric porphyrin/thiosulfate ratio.…”

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confidence: 59%

Electrochemistry and spectroscopy of sulfate and thiosulfate complexes of iron porphyrins

Crawford

2002

Inorganica Chimica Acta

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Abstract:The electrochemical and spectroscopic properties of the complex formed by the addition of thiosulfate to ferric porphyrins were examined. The NMR spectrum of the thiosulfate-ferric porphyrin complex was consistent with a high-spin ferric complex, while the EPR spectrum at liquid nitrogen temperatures indicated that the complex under these conditions was low-spin. Such behavior has been previously observed for other ferric-porphyrin complexes. The visible spectra were characterized by a shift in the Soret band to higher energies, with smaller changes in the longer wavelength region. The complex was reasonably stable in DMF, but slowly reduced over several hours to Fe II (TPP) and S4O6 2-. The voltammetric behavior of the thiosulfate complex in DMF consists of two waves, the first of which was irreversible. The

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“…2A) is selectively perturbed in the Fe(III) G117I CooA variant. The rhombicity (expressed as E/D (26)) of G117I CooA is comparable to that of a model heme-thiolate complex (Table II ( 27)), although it is a bit lower than those of Fe(III) fivecoordinate, high spin thiolate-ligated hemoproteins such as cytochrome P450cam (P-450cam (28)), endothelial nitric oxide synthase (26), and chloroperoxidase (29) (Table II). On the other hand, the rhombicity of G117I CooA is significantly higher than those of nitrogen-based ligand high spin signal such as FixL (30) and soluble guanylyl cyclase (31).…”

Section: Ligation Structure and In Vivo Activity Of Glymentioning

confidence: 88%

The Heme Pocket Afforded by Gly117 Is Crucial for Proper Heme Ligation and Activity of CooA

Youn¹,

Kerby²,

Thorsteinsson³

et al. 2001

Journal of Biological Chemistry

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Axial ligation modes in iron(III) porphyrins. Models for the oxidized reaction states of cytochrome P-450 enzymes and the molecular structure of iron(III) protoporphyrin IX dimethyl ester p-nitrobenzenethiolate

Cited by 216 publications

References 10 publications

Structures of Thiolate- and Carboxylate-Ligated Ferric H93G Myoglobin: Models for Cytochrome P450 and for Oxyanion-Bound Heme Proteins^,

Structures of Thiolate- and Carboxylate-Ligated Ferric H93G Myoglobin: Models for Cytochrome P450 and for Oxyanion-Bound Heme Proteins^,

Electrochemistry and spectroscopy of sulfate and thiosulfate complexes of iron porphyrins

The Heme Pocket Afforded by Gly117 Is Crucial for Proper Heme Ligation and Activity of CooA

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Axial ligation modes in iron(III) porphyrins. Models for the oxidized reaction states of cytochrome P-450 enzymes and the molecular structure of iron(III) protoporphyrin IX dimethyl ester p-nitrobenzenethiolate

Cited by 216 publications

References 10 publications

Structures of Thiolate- and Carboxylate-Ligated Ferric H93G Myoglobin: Models for Cytochrome P450 and for Oxyanion-Bound Heme Proteins,

Structures of Thiolate- and Carboxylate-Ligated Ferric H93G Myoglobin: Models for Cytochrome P450 and for Oxyanion-Bound Heme Proteins,

Electrochemistry and spectroscopy of sulfate and thiosulfate complexes of iron porphyrins

The Heme Pocket Afforded by Gly117 Is Crucial for Proper Heme Ligation and Activity of CooA

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Structures of Thiolate- and Carboxylate-Ligated Ferric H93G Myoglobin: Models for Cytochrome P450 and for Oxyanion-Bound Heme Proteins^,

Structures of Thiolate- and Carboxylate-Ligated Ferric H93G Myoglobin: Models for Cytochrome P450 and for Oxyanion-Bound Heme Proteins^,