Structural factors that influence functional properties are examined in the case of four heme enzymes: cytochrome P-450, chloroperoxidase, horseradish peroxidase, and secondary amine mono-oxygenase. The identity axial ligand, nature environment, steric accessibility iron edge combine to play major roles determining reactivity each enzyme. importance synthetic porphyrin models understanding protein-free metal center is emphasized. conclusions described herein have been derived from studies at...

With the use of x-ray absorption spectroscopy, we have found that Fe-O bond in chloroperoxidase compound II (CPO-II) is much longer than expected for an oxoiron(IV) (ferryl) unit; notably, experimentally determined length 1.82(1) Å accords closely with density functional calculations on a protonated ferryl (Fe IV -OH, 1.81 Å). The basicity CPO-II [p K > 8.2 (where acid dissociation constant)] attributable to strong electron donation by axial thiolate. We suggest good model rebound...

An extensive series of ligand complexes ferric cytochrome P-450-CAM has been examined by UV-visible absorption, magnetic circular dichroism, and electron paramagnetic resonance spectroscopy in an attempt to identify the trans cysteinate six-coordinate resting state enzyme. Thus, ligands used have chosen serve as models for coordination potential endogenous amino acids include alcohol, amide carboxylate oxygen donors, amine, imidazole indole nitrogen donors disulfide, thioether, thiol,...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructural characterization of horseradish peroxidase using EXAFS spectroscopy. Evidence for Fe = O ligation in compounds I and IIJames E. Penner-Hahn, Kim. Smith Eble, Thomas J. McMurry, Mark. Renner, Alan L. Balch, John T. Groves, H. Dawson, Keith O. HodgsonCite this: Am. Chem. Soc. 1986, 108, 24, 7819–7825Publication Date (Print):November 1, 1986Publication History Published online1 May 2002Published inissue 1 November...

Abstract A new time‐of‐flight mass analyser compatible with conventional continuous ionization methods is described. resolution at m / z 2000 of m/Δm >2000 (50% valley) predicted for the instrument which presently being prototyped. Sensitivity advantages over scanning instruments are also this instrument.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSpectroscopic studies of stellacyanin, plastocyanin, and azurin. Electronic structure the blue copper sitesEdward I. Solomon, Jeffrey W. Hare, David M. Dooley, John H. Dawson, Philip J. Stephens, Harry B. GrayCite this: Am. Chem. Soc. 1980, 102, 1, 168–178Publication Date (Print):January 1980Publication History Published online1 May 2002Published inissue 1 January...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagnetic circular dichroism studies. 43. Oxidized cytochrome P-450. Magnetic evidence for thiolate ligation in the substrate-bound form. Implications catalytic mechanismJohn Harold Dawson, R. H. Holm, James Trudell, Guenther Barth, Robert E. Linder, Edward Bunnenberg, Carl Djerassi, and S. C. TangCite this: J. Am. Chem. Soc. 1976, 98, 12, 3707–3709Publication Date (Print):June 1, 1976Publication History Published online1 May 2002Published inissue 1...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFunctionalized nitrogen atom transfer catalyzed by cytochrome P-450Edmund W. Svastits, John H. Dawson, Ronald Breslow, and Samuel GellmanCite this: J. Am. Chem. Soc. 1985, 107, 22, 6427–6428Publication Date (Print):October 1, 1985Publication History Published online1 May 2002Published inissue 1 October 1985https://doi.org/10.1021/ja00308a064RIGHTS & PERMISSIONSArticle Views1338Altmetric-Citations139LEARN ABOUT THESE METRICSArticle Views are the...

The binding of thiol, thiolate, thioether, and disulfide sulfur donor ligands to ferric cytochrome P-450-CAM myoglobin has been investigated by W-visible absorption, magnetic circular dichroism (MCD), EPR spectroscopy.For P-450, the all donors is competitive with substrate binding.Addition thiols P-450 leads interconvertible thiol or thiolate-bound species depending on acidity ( p a ) solution pH; ligation lowers their pK, about 4 units.In contrast, only form seen for regardless pH...

The T252A mutant of cytochrome P450cam is unable to form the oxoferryl "active oxygen" intermediate, as judged by its inability hydroxylate normal substrate, camphor. In present study, we demonstrate that nonetheless able epoxidize olefins, due action a second oxidant. However, shown in earlier radiolytic studies and ability reduce dioxygen hydrogen peroxide, retains hydroperoxo−ferric reaction cycle intermediate. results provide strong evidence P450 can serve electrophilic oxidant capable...

Cysteine plays a key role as metal ligand in metalloproteins. In all well-recognized cases, however, it is the anionic cysteinate that coordinates. Several cysteinate-ligated heme proteins are known, but some fail to retain thiolate ligation ferrous state, possibly following protonation form neutral cysteine. Ligation by cysteine thiol has not been documented. To establish spectroscopic signatures for such systems, we have prepared five-coordinate adducts of myoglobin H94G cavity mutant with...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStudies of the ferric forms cytochrome P-450 and chloroperoxidase by extended x-ray absotption fine structure. Characterization iron-nitrogen iron-sulfur distancesStephen P. Cramer, John H. Dawson, Keith O. Hodgson, Lowell HagerCite this: J. Am. Chem. Soc. 1978, 100, 23, 7282–7290Publication Date (Print):November 1, 1978Publication History Published online1 May 2002Published inissue 1 November...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStudies of the Heme Coordination and Ligand Binding Properties Soluble Guanylyl Cyclase (sGC): Characterization Fe(II)sGC Fe(II)sGC(CO) by Electronic Absorption Magnetic Circular Dichroism Spectroscopies Failure CO To Activate EnzymeJudith N. Burstyn, Anita E. Yu, Elizabeth A. Dierks, Barton K. Hawkins, John H. DawsonCite this: Biochemistry 1995, 34, 17, 5896–5903Publication Date (Print):May 2, 1995Publication History Published online1 May...

Reactions of substrate-free ferric cytochrome P450cam with peracids to generate Fe=O intermediates have previously been investigated contradictory results. Using stopped-flow spectrophotometry, the reaction m-chloroperoxybenzoic acid demonstrated an Fe(IV)=O + porphyrin pi-cation radical (Cpd I) (Egawa, T., Shimada, H., and Ishimura, Y. (1994) Biochem. Biophys. Res. Commun. 201, 1464-1469). By contrast, peracetic acid, plus a tyrosyl were observed by freeze-quench Mossbauer EPR spectroscopy...

In order to further elucidate the electronic structure and ligand coordination properties of cytochrome P-450, we have performed a search for anions which can bind heme P-450-CAM purified from Pseudomonas putida The complexes been characterized by W-visible absorption electron paramagnetic resonance spectroscopy.W e found that (a) relatively wide variety (L-) are well known ligands ferric myoglobin, including CN-, N3-, RS-, RCOO-, SCN-, SeCN-, OCN-, reversibly P-450 form bis-anionic...

X-ray absorption edge and extended x-ray fine structure studies have been undertaken on resting (ferric) horseradish peroxidase, HRP compound I (HRP-I), I1 (HRP-11), several highly oxidized synthetic iron porphyrins that may relevance as models for the site in peroxidase.The energies of edges are consistent with an Fe(1V) formulation species.The shapes further support assignment HRP-I one model compounds Fe(IV)-porphyrin m-cations.The also demonstrate sites not identical to...

The hydroxylation of (1R)-camphor by cytochrome P450-CAM involves almost complete coupling electron to oxygen transfer. Modifications at C-5 camphor, the normal site P450-CAM, lead as much 98% uncoupling and transfer well decreases in rate uptake (up 10-fold) oxygenated product formation 210-fold). Two modes are seen: (a) two-electron which decrease is balanced increases H2O2 (b) four-electron "oxidase" where NADH/O2 ratio has changed from one nearly two relatively little formed. Both...

Reconstitution of the endothelial nitric oxide synthase heme domain (NOS) with catalytically noncompetent 4-aminotetrahydrobiopterin has allowed us to prepare at −40 °C oxyferrous-NOS−substrate complexes both l-arginine (Arg) and NG-hydroxyarginine (NOHA). We have radiolytically cryoreduced these 77 K used EPR ENDOR spectroscopies characterize initial products reduction, as well intermediates that arise during stepwise annealing higher temperatures. Peroxo-ferri-NOS is primary product...

The heme uptake systems by which bacterial pathogens acquire and utilize have recently been described. Such may directly from the host's hemeproteins or via a hemophore that sequesters transports to an outer membrane receptor subsequently translocating proteins is further transported into cell. However, little known of binding release mechanisms facilitate pathogenic organism. As first step toward elucidating molecular level events drive release, we undertaken spectroscopic mutational study...

Cytochrome P450cam was subjected to high pressures of 2.2 kbar, converting the enzyme its inactive form, P420cam. The resultant protein characterized by electron paramagnetic resonance, magnetic circular dichroism, and electronic absorption spectroscopy. A range exogenous ligands has been employed probe coordination structure results suggest that conversion P420cam involves a conformational change which restricts substrate binding site and/or alters ligand access channel. reduction potential...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLigand and halide binding properties of chloroperoxidase: peroxidase-type active site heme environment with cytochrome P-450 type endogenous axial ligand spectroscopic propertiesMasanori Sono, John H. Dawson, Lowell P. HagerCite this: Biochemistry 1986, 25, 2, 347–356Publication Date (Print):January 28, 1986Publication History Published online1 May 2002Published inissue 28 January...

As described under "Results," addition of nitroalkanes to P-450 reducing conditions probably does not yield a nitroalkane complex.Mansuy et al. (17, 18) suggest that the product is ferrous nitrosoalkane complex.