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Pseudoazurin binds at a single site on cytochrome c peroxidase from Paracoccus pantotrophus with a K(sub d) of 16.4 MuM at 25 degree C, pH 6.0, in an endothermic rdcytochromeeaction that is driven by a large entropy change. Cytochrome c550 and pseudoazurin bind at the same site on the cytochrome c peroxidase and that the pair of electrons required restoring the enzyme to its active state after turnover are delivered one-by-one to the electron-transferring heme.

Research has been conducted on the murine ferrochetalase. The use of the resonance Raman spectroscopy in investigating interactions of the inhibitor and porphyrin substrates with murine ferrochetalase is discussed.

Research has been conducted on the heme macrocycle and substituents. Their structural changes caused by the binding of Ca (super)2+ to the diheme cytochrome c peroxidase from Paracoccus pantotrophus have been investigated using resonance Raman spectroscopy.

Isoniazid antibiotic activation by the KatG heme enzyme may occur via a cytochrome p450-like mechanism suggesting the importance of redox potential in the enzyme's resistance to the antibiotic. Data indicate that the redox potential of Mycobacterium tuberculosis KatG heme enzyme is similar to typical hemoproteins.

Research has been conducted on the Pseudomonas nautica 617 nitrous oxide reductase. The aerobic purification of this reductase has been examined.

Research has been conducted on the xanthine oxidase family molybdoenzymes that contain two clusters. The X-ray crystal structure of the clusters has been investigated.

Researchers report one of the few known sulfate-reducing bacteria that uses tungsten-containing formate dehydrogenase. Most other sulfate-reducing bacteria use molybdenum in this enzyme. In Desulfovibrio gigas, the tungsten is coordinated via two molybdopterin guanine dinucleotide cofactors.

A study was conducted to characterize the purification, biochemical and spectroscopic determination of adenosine triphosphates (ATP) from a couple of Desulfovibrio species. The enzymes, which were categorized as metalloproteins, supported cobalt, zinc and metal ligation. Experimental results indicated that the molecular masses of native ATPs differed with the Desulfovibrio species. Findings also showed that the proteins were related to the families of Zn-containing enzymes and Co-containing enzymes.

Conformational differences in the hemes in ferricytochromes c(sub3) have been investigated using resonance Raman spectroscopy, molecular mechanics calculations and normal-coordinate structural decomposition techniques. The observed nonplanarity is mainly due to a fingerprint peptide segment, and factors influencing the folding pattern of the fingerprint peptide and other peptide-heme contacts also have an effect on heme conformation.

Mossbauer and EPR spectroscopies were used to characterize the Fe clusters in an Fe-S protein isolated from Desulfovibrio desulfuricans (ATCC 27774). This protein was previously thought to contain hexanuclear Fe clusters, but a recent X-ray crystallographic measurement on a similar protein isolated from Desulfovibrio vulgaris showed that the protein contains two tetranuclear clusters, a cubane-type [4Fe-4S] cluster and a mixed-ligand cluster of novel structure [Lindley et al. (1997) Abstract, Chemistry of Metals in Biological Systems, European Research Conference, Tomar, Portugal]. Three protein samples poised at different redox potentials (as-purified, 40 and 320 mV) were investigated. In all three samples, the [4Fe-4S] cluster was found to be present in the diamagnetic 2+ oxidation state and exhibited typical Mossbauer spectra. The novel-structure cluster was found to be redox active. In the 320-mV and as-purified samples, the cluster is at a redox equilibrium between its fully oxidized and one-electron reduced states. In the 40-mV sample, the cluster is in a two-electron reduced state. Distinct spectral components associated with the four Fe sites of cluster 2 in the three oxidation states were identified. The spectroscopic parameters obtained for the Fe sites reflect different ligand environments, making it possible to assign the spectral components to individual Fe sites. In the fully oxidized state, all four iron ions are high-spin ferric and antiferromagnetically coupled to form a diamagnetic S = 0 state. In the one-electron and two-electron reduced states, the reducing electrons were found to localize, consecutively, onto two Fe sites that are rich in oxygen/nitrogen ligands. based on the X-ray structure and the Mossbauer parameters, attempts could be made to identify the reduced Fe sites. For the two-electron reduced cluster, EPR and Mossbauer data indicate that the cluster is paramagnetic with a nonzero interger spin. For the one-electron reduced cluster, the data suggest a half-integer spin of 9/2. Characteristic fine and hyperfine parameters for all four Fe sites were obtained. Structural implications and the nature of the spin-coupling interactions are discussed.

The x-ray crystallographic structure of cytochrome c3 from the bacterium Desulfovibrio desulfuricans ATCC 27774 using a molecular replacement method reveals a similarity in structure to cytochromes from other bacteria with regard to the distances and angles between heme residues. The crystallographic structure is useful in determining the structural characteristics necessary for electron transfer in cytochromes.

The binding of 2,7,9-tricarboxy-1H-pyrrolo(2,3-f)quinoline-4,5-dione (PQQ) to the apoenzyme quinohemoprotein ethanol dehydrogenase (QH-EDH) from Comamonas testosteroni produces a compact enzyme conformation that catalyzes rapid transfer of electrons within the molecule. PQQ binding causes rotation of the methionine ligand of heme c and an increase in the density of electrons on one of the pyrrole rings. The heme's midpoint redox potential also increases. The enzyme QH-EDH is obtained when C. testosteroni is grown on ethanol, but the enzyme is inactive, in apo form with only the heme c portion, until binding to PQQ takes place to form the holoenzyme.

Anaerobic titrations of reduced cytochrome c3 with flavodoxin reveal a stoichiometry of 4 moles of flavodoxin in the oxidization of the tetraheme cytochrome. Anaerobic stopped flow methods help study the kinetic properties of electron transfer. Electron transfer occurs between reduced Desulfovibrio vulgaris cytochrome c3 and Desulfovibrio vulgaris flavodoxins. The oxidization reaction involving electron transfer produces only neutral flavodoxin semiquinone and oxidized cytochrome c3.

H-NMR and molecular modeling studies of electron-transfer proteins reveal the ternary complex property of flavodoxin and cytochrome c3 proteins. Interaction between flavodoxin and cytochromes c3 indicate the binding of two cytochrome c3 molecules to every flavodoxin molecule. Protein-protein titrations at specific proton NMR signals explain a binding model for this complex, with stoichiometry and binding constants.

A novel Mo-Fe protein (MorP) associated with a system that responds to Mo in Desulfovibrio alaskensis is characterized. This protein has represented the first system associated with molybdenum response in sulfate reducing bacteria and as its expression has responded to Mo, it is called as molybdenum response associated protein (MorP).

The multicopper sites in the nitrous oxide reductase in the Pseudomonas nautica accept electrons form the physiological electron donor cytochrome [c.sub.552]. Chemical kinetic studies, nuclear magnetic resonance and a molecular docking program (BiGGER) show the hydrophobic nature of this reaction and presence of copper center in the electron transfer.

The first resonance Raman studies of the mixed-valence and fully reduced forms of Paracoccus pantrotrophus bacterial cytochorme c peroxidase are reported. The results from Raman spectra provide insight into the effects of reduction and calcium ion binding on the coordination and spin states of the hemes of the enzymes.

The positive vector of the very large dipole moment of pseudoazurin from Paracoccus pantotrophus LMD 52.44 is positioned at the putative electron-transfer site, His81, and is shown to be instrumental in preorientation of the molecule against the negatively charged cytochrome c peroxidase. It is suggested that these acidic residues moderate the electrostatic influence of the lysines and so ensure that specific charge interactions do not form across the interface with the peroxidase.

Examines the nature and properties of the complex electron-transfer chain formed between flavodoxin and cytochrome c3. Nuclear magnetic resonance protein titrations; Prediction of protein structure by homology modeling; Analysis of the surface electrostatic potentials; Computer graphics modeling of the complex.