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Results show an anisotropic decay of substrates bound to cytochrome P450(sub)cam, indicating that the substrate mobility is influenced by physicochemical and protein-substrate interactions at the local active sites. Furthermore, the cytochrome's local and peripheral structural amenability and heterogeneity coupled with substrate mobility regulate substrate binding orientation during enzyme catalysis.

Crystal structure analysis of mitochondrial cytochrome bc1 and famoxadone inhibitor complex reveals that the aromatic-aromatic interactions serve as structural bases for specific protein-ligand interactionin a hydrophobic environment. Data indicate that cytochrome b has a functional role as seen by marked conformational changes in cytochrome b and iron sulfur protein subunit of the complex.

Using a combination of Mössbauer spectroscopy and density functional calculations, we have determined that the ferryl forms of P450BM3 and P450cam are protonated at physiological pH. Density functional calculations were performed on large active-site models of these enzymes to determine the theoretical Mössbauer parameters for the ferryl and protonated ferryl (FeIVOH) species. These calculations revealed a significant enlargement of the quadrupole splitting parameter upon protonation of the ferryl unit. The calculated quadrupole splittings for the protonated and unprotonated ferryl forms of P450BM3 are ΔEQ = 2.17 mm/s and ΔEQ = 1.05 mm/s, respectively. For P450cam, they are ΔEQ = 1.84 mm/s and ΔEQ = 0.66 mm/s, respectively. The experimentally determined quadrupole splittings (P450BM3, ΔEQ = 2.16 mm/s; P450cam, ΔEQ = 2.06 mm/s) are in good agreement with the values calculated for the protonated forms of the enzymes. Our results suggest that basic ferryls are a natural consequence of thiolate-ligated hemes. [ABSTRACT FROM AUTHOR]

Electrospray ionization in combination with Fourier transform ion cyclotron resonance spectrometry is used to prepare and characterize at a molecular level high-valent oxoiron intermediates formed in the reaction of [(TPFPP)FeIII]Cl (TPFPP= meso-tetrakis(pentafluorophenyl)porphinato dianion) (1-Cl) with H2O2 in methanol. The intrinsic reactivity in the gas phase of the iron(IV) oxo porphyrin cation radical complex, [(TPFPP)·+FeIV=O]+, has been probed toward selected substrates (S), chosen among naturally occurring and model compounds. Whereas CO and cyclohexane proved to be unreactive, olefins, sulfides, amines, and phosphites all undergo oxygen atom transfer in the gas phase yielding the reduction product 1 and/or an adduct ion ([1-S]+). The reaction efficiencies show a qualitative correlation with the oxophilic character of the active site of S. A notable exception is nitric oxide, which displays a remarkably high reactivity, in line with the important role of NO reactions with iron porphyrin complexes. Furthermore, subsidiary information on the neat association reaction of 1 with selected ligands (L) has been obtained by a kinetic study showing that both the efficiency and the extent of ligation toward the naked ion 1 depend on the electron-donating ability of L. [ABSTRACT FROM AUTHOR]

Focuses on the theoretical perspective on the structure and mechanism by cytochrome P450 enzymes. Description of cytochrome P450 enzymes; Advantage of the advances in density functional theory; Presentation of the coverage, sources of computational results, and models of the enzyme.

Studies the structure and chemistry of cytochrome P450. Emphasis on the role of cytochrome P450 in biology; Presence of the cytochrome P450 in all branches of the tree of life that catalogs the diversity of life forms; Discussion on the formation of the peroxol/hydroperoxo complex.

Recent spectroscopic, kinetics, and structural studies on cytochrome c oxidases (CcOs) suggest that the histidine-tyrosine cross-link at the heme a3—CuB binuclear active site plays a key role in the reductive O2-cleavage process. In this report, we describe dioxygen reactivity of copper and heme/Cu assemblies in which the imidazole—phenol moieties are employed as a part of copper ligand LN4OH (2-{4-[2-(bis-pyridin-2-ylmethyl-amino)-ethyl]-imidazol-1-yl}-4,6-di -tert-butyl-phenol). Stopped-flow kinetic studies reveal that low-temperature oxygenation of [Cul(LN4OH)]+ (1) leads to rapid formation of a copper-superoxo species [Cull(LN4OH)(O2-)]+ (1a), which further reacts with 1 to form the 2:1 Cu:O2 adduct, peroxo complex [{Cull(LN4OH)}2(O22-)]22+ (1b). Complex 1b is also short-lived, and a dimer Cu(II)-phenolate complex [CuII(LN4O-)]22+ (1c) eventually forms as a final product in the later stage of the oxygenation reaction. Dioxygen reactivities of 1 and its anisole analogue [CuI(LN4OMe)]+ (2) in the presence of a heme complex (F8)FeII (3) (F8 = tetrakis(2,6,-difluorotetraphenyl)-porphyrinate) are also described. Spectroscopic investigations including UV-vis, 1H and 2H NMR, EPR, and resonance Raman spectroscopies along with spectrophotometric titration reveal that low-temperature oxygenation of 1/3 leads to formation of a heme-peroxo-copper species [(F8)FeIII-(O22 )-CuII(LN4OH)]+ (4), v(o-o) = 813 cm-1 Complex 4 is an S = 2 spin system with strong antiferromagnetic coupling between high-spin iron(III) and copper(II) through a bridging peroxide ligand. A very similar complex [(F8)FeIII-(O22- )-CuII(LN4OMe)]+ (5) (v(o-o) = 815 cm-1) can be generated by utilizing the anisole compound 2, which indicates that the cross-linked phenol moiety in 4 does not interact with the bridging peroxo group between heme and copper. This investigation thus reveals that a stable heme-peroxo-copper species can be generated even in the presence of an imidazole-phenol group (i.e., possible electron/proton donor source) in close proximity. Future studies are needed to probe key factors that can trigger the reductive O-O cleavage in CcO model compounds. [ABSTRACT FROM AUTHOR]

The cytochrome b6 conjugation site for dicyclohexylcarbodiimide (DCCD) was determined through selective digestion and nucleotide sequencing of labeled peptide fragments. Trypsin digestion produced a 12.5 kilodalton fragment containing the labeled DCCD and the heme moiety. On the other hand, chymotrypsin digestion produced a 17 kilodalton fragment. Nucleotide sequence analysis show that DCCD is bound to either aspartate or glutamate at positions 155 and 166 respectively.

Presents the study on the contact shifts and magnetic tensor orientation in Rhodobacter capsulatus ferrocytochrome. Magnetic susceptibility studies of Rhodobacter capsulatus ferrocytochrome; Determination of the differences in chemical shift; Orientation and anisotropy of the paramagnetic susceptibility tensor; Paramagnetic chemical shifts of heme protons.

Results demonstrate the infrared redox difference spectra of the bovine mitochondrial bc(sub)1 complex components using attenuated total reflection (ATR)-FTIR spectroscopy. Data indicate that the spectra are due to the perturbations of the prosthetic groups and the surrounding protein.

Research describes biochemical characterization and phylogenetic relationship of a naphthoquinol oxidizing cytochrome bc(sub)1 complex from Aquifex aeolicus by comparing it with other Rieske/cyt b, bc complexes from proteobacteria. The enzyme contains hemes b(sub)1 and C(sub)1 and two distinct Rieske center of the cytochrome bc(sub)1 complex. Phylogenetically it represents the only extant naphthoquinol oxidizing true cytochrome bc(sub)1 complex among proteobacteria.

Research has been conducted on NADPH-cytochrome P450 reductase, a flavoprotein containing FAD and FMN cofactors. Results demonstrate the ability of this flavoprotein to donate a single electron to its redox partners, and confirm that it is a tool for investigating electron-transfer properties of intact reductase molecule.

Results indicate that Phormidium laminosum cytochrome f surface charge is neutralized at five acidic residues when the cytochrome f reacts with plastocyanin. Data indicate that these acidic regions are likely to be involved in an electrostatic interaction, similar to the interactions seen with higher plant proteins.

Research reveals that 75% of the differences in the reaction between cytochrome f and plastocyanin from plants and the cyanobacterium is contributed by the N-terminal heme-shielding peptide in the absence of electrostatic interactions.