Proton NMR study of coordinated imidazoles in low-spin ferric heme complexes. Assignment of single proton histidine resonance in hemoproteins

Gn, La Mar; Js, Frye; Jd, Satterlee

doi:10.1016/0304-4165(76)90110-0

Cited by 40 publications

(10 citation statements)

References 20 publications

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“…Since the chemical shifts of the new peaks differ from those of diimidazolehemin (4),3c we assign them to four methyl resonances of monocyanomonoimidazole hemin (5). This assignment is consistent with the recent report by La Mar et al 22 When the imidazole:cyanide:hemin ratio is about 1.5:1.5:1, the signal of 2 was completely lost and the relative areas of species 3 and 5 were 0.17 and 0.83, respectively. Further addition of imidazole, up to an imidazole:cyanide:hemin ratio of 8:1.5:1, resulted in a total loss of signals from 3 and no trace of 4.…”

Section: Resultssupporting

confidence: 93%

Proton nuclear magnetic resonance study of equilibriums and paramagnetisms of ferriprotoporphyrin IX-ligand complexations

Wang¹,

Yeh²,

Johnson³

1978

J. Am. Chem. Soc.

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Section: Resultssupporting

confidence: 93%

Proton nuclear magnetic resonance study of equilibriums and paramagnetisms of ferriprotoporphyrin IX-ligand complexations

Wang¹,

Yeh²,

Johnson³

1978

J. Am. Chem. Soc.

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“…Further upfield in each spectrum is the broad single proton resonance that, on the basis of studies of both model systems and other ferriheme proteins, has been assigned to the heme-coordinated histidine La Mar et al, 1976, 1982. For wild-type native CcP it is His-175 CelH (Figure 1).…”

Section: Resultsmentioning

confidence: 99%

Comparative proton NMR analysis of wild-type cytochrome c peroxidase from yeast, the recombinant enzyme from Escherichia coli, and an Asp-235 .fwdarw. Asn-235 mutant

Jd¹,

Je²,

Jm³

et al. 1990

Biochemistry

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Proton NMR spectra of cytochrome c peroxidase (CcP) isolated from yeast (wild type) and two Escherichia coli expressed proteins, the parent expressed protein [CcP(MI)] and the site-directed mutant CcP(MI,D235N) (Asp-235----Asn-235), have been examined. At neutral pH and in the presence of only potassium phosphate buffer and potassium nitrate, wild-type Ccp and CcP(MI) demonstrate nearly identical spectra corresponding to normal (i.e., "unaged") high-spin ferric peroxidase. In contrast, the mutant protein displays a spectrum characteristic of a low-spin form, probably a result of hydroxide ligation. Asp-235 is hydrogen-bonded to the proximal heme ligand, His-175. Changing Asp-235 to Asn results in alteration of the pK for formation of the basic form of CcP. Thus, changes in proximal side structure mediate the chemistry of the distal ligand binding site. All three proteins bind F-, N3-, and CN- ions, although the affinity of the mutant protein (D235N) for fluoride ion appears to be much higher than that of the other two proteins. Analysis of proton NMR spectra of the cyanide ligated forms leads to the conclusion that the mutant protein (D235N) possesses a more neutral proximal histidine imidazole ring than does either wild-type CcP or CcP(MI). It confirms that an important feature of the cytochrome c peroxidase structure is at least partial, and probably full, imidazolate character for the proximal histidine (His-175).

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“…All the proton chemical shifts could be assigned by following the changes with temperature in the spectra of FeTPPCl complexes with the symmetric ligands ( 1, 2, 3 or 6 ) because of simplification owing to their C 2 symmetry. Complexes of FeDMPPCl were compared to previously reported systems in order to resolve the chemical shifts in the high ( δ <0) and low ( δ >10 ppm) field spectra 45. Interestingly, for the spectrum of the nonsymmetric complex 7 ‐FeTPPCl, one can also assign the peaks of protons in the vicinity of the paramagnetic center.…”

Section: Resultsmentioning

confidence: 99%

“…Complexes of FeDMPPCl were compared to previously reported systems in order to resolve the chemical shifts in the high (d < 0) and low (d > 10 ppm) field spectra. [45] Interestingly, for the spectrum of the nonsymmetric complex 7-FeTPPCl, one can also assign the peaks of protons in the vicinity of the paramagnetic center. Different chemical shifts were observed for the two C2-bound imidazole protons (d À 7.8 and À 15.6 ppm, [D 7 ]DMF, 240 K) and for the CH 2 -imidazole protons (d 17.9 and 19.2 ppm), which are located on opposite arms of the ligand.…”

Section: Design and Synthesismentioning

confidence: 99%

Bidentate Ligation of Heme Analogues; Novel Biomimetics of the Peroxidase Active Site

et al. 2002

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The multifunctional nature of proteins that have iron–heme cofactors with noncovalent histidine linkage to the protein is controlled by the heme environment. Previous studies of these active‐site structures show that the primary difference is the length of the iron‐proximal histidine bond, which can be controlled by the degree of H‐bonding to this histidine. Great efforts to mimic these functions with synthetic analogues have been made for more than two decades. The peroxidase models resulted in several catalytic systems capable of a large range of oxidative transformations. Most of these model systems modified the porphyrin ring covalently by directly binding auxiliary elements that control and facilitate reactivity; for example, electron‐donating or ‐withdrawing substituents. A biomimetic approach to enzyme mimicking would have taken a different route, by attempting to keep the porphyrin ring system unaltered, as close as possible to its native form, and introducing all modifications at or close to the axial coordination sites. Such a model system would be less demanding synthetically, would make it easy to study the effect of a single structural modification, and might even provide a way to probe effects resulting from porphyrin exchange. We introduce here an alternative model system based on these principles. It consists of a two component system: a bis‐imidazolyl ligand and an iron–porphyrin (readily substituted by a hemin). All modifications were introduced only to the ligand that engulfs the porphyrin and binds to the iron's fifth and sixth coordination sites. We describe the design, synthesis, and characterization of nine different model compounds with increased complexity. The primary tool for characterizing the environment of each complex FeIII center was the Extended X‐ray Absorption Fine Structure (EXAFS) measurements, supported by UV/Vis, IR, and NMR spectroscopy and by molecular modeling. Introduction of asymmetry, by attaching different imidazoles as head groups, led to the formation of two axial bonds of different length. Addition of H‐bonds to one of the imidazoles in an advanced model increased this differentiation and expanded the porphyrin ring. These complexes were found to be almost identical in structure to peroxidase active sites. Similarly to the peroxidases and other synthetic models, these compounds stabilize the green, compound I‐like intermediate, and catalyze the oxidation of organic substrates.

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Proton NMR study of coordinated imidazoles in low-spin ferric heme complexes. Assignment of single proton histidine resonance in hemoproteins

Cited by 40 publications

References 20 publications

Proton nuclear magnetic resonance study of equilibriums and paramagnetisms of ferriprotoporphyrin IX-ligand complexations

Proton nuclear magnetic resonance study of equilibriums and paramagnetisms of ferriprotoporphyrin IX-ligand complexations

Comparative proton NMR analysis of wild-type cytochrome c peroxidase from yeast, the recombinant enzyme from Escherichia coli, and an Asp-235 .fwdarw. Asn-235 mutant

Bidentate Ligation of Heme Analogues; Novel Biomimetics of the Peroxidase Active Site

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