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C J Batie

Publications and source records attributed to C J Batie.

15 recordsLinked to original sources
PubMed1999

Electron paramagnetic resonance measurements of the ferrous mononuclear site of phthalate dioxygenase substituted with alternate divalent metal ions: direct evidence for ligation of two histidines in the copper(II)-reconstituted protein.

The metalloenzyme phthalate dioxygenase (PDO) contains two iron-based sites. A Rieske-type [2Fe-2S] cluster serves as an electron-transferring cofactor, and a mononuclear iron site is the putative site of substrate oxygenation. A reductase, which contains FMN and a plant-type [2Fe-2S] ferredoxin domain, transfers electrons from NADH to the Rieske center. Any of the metal ions, Fe(II), Cu(II), Co(II), Mn(II), and Zn(II), can be used to populate the mononuclear site, but only Fe(II) is competent for effecting hydroxylation. Nevertheless, studies of how these metal ions affect both the EPR spectra of the reduced Rieske site and the kinetics of electron transfer in the PDO system indicated that each of these metal ions binds tightly and affects the protein similarly. In this study, EPR spectra were obtained from samples in which iron of the mononuclear site was replaced with Cu(II). The use of (63)Cu(II), in combination with PDO obtained from cultures grown on media enriched in (15)N [using ((15)NH(4))(2)SO(4) as a sole nitrogen source], [delta,epsilon-(15)N]histidine, as well as natural abundance sources of nitrogen, enabled detailed spectral analysis of the superhyperfine structure of the Cu(II) EPR lines. These studies clearly show that two histidines are coordinated to the mononuclear site. Coupled with previous studies [Bertini, I., Luchinat, C., Mincione, G., Parigi, G., Gassner G. T., and Ballou, D. P. (1996) J. Bioinorg. Chem. 1, 468-475] that show the presence of one or two water molecules coordinated to the iron, it is suggested that the mononuclear site is similar to several other mononuclear nonheme iron proteins, including naphthalene dioxygenase, for which crystal structures are available. The lack of observable EPR interaction signals between Cu(II) in the mononuclear site and the reduced Rieske center of PDO suggest that the two sites are at least 12 A apart, which is similar to that found in the naphthalene dioxygenase crystal structure.

Apoenzymes↗
PubMed1998

Interactions among P450 enzymes when combined in reconstituted systems: formation of a 2B4-1A2 complex with a high affinity for NADPH-cytochrome P450 reductase.

The purpose of this study is to characterize the interactions among P450 1A2, P450 2B4, and P450 reductase in mixed reconstituted systems. Previously, our laboratory demonstrated that in the presence of certain substrates, 1A2 can influence the catalytic characteristics of 2B4 [Cawley et al. (1995) Biochemistry 34, 1244-1247]. The goal of the current study is to distinguish between two models to explain these interactions: one model where substrate increases the affinity of one P450 enzyme for the reductase, and another model where substrate increases the affinity of one P450 for the reductase through the formation of a 1A2-2B4 complex. According to this model, the 1A2 moiety of 1A2-2B4 forms a high-affinity complex with reductase. Reductase, 1A2, and 2B4 were reconstituted with dilauroylphosphatidylcholine, and the effect of reductase concentration on 7-pentoxyresorufin-O-dealkylation was examined with 2B4-reductase and 1A2-reductase binary systems, and in ternary systems containing different 2B4:1A2 ratios. At subsaturating [reductase], there was a dramatic inhibition of the 2B4-dependent activity in the ternary system as compared with the binary systems. These results are consistent with the formation of a ternary (reductase-1A2-2B4) complex where the reductase is bound specifically to 1A2. At higher reductase concentrations where the reductase-binding sites on 1A2 become saturated, the results are consistent with the formation of a quaternary complex in which reductase binds to both P450 enzymes (reductase-1A2-2B4-reductase). Analogous experiments using the 1A2-preferred substrate 7-ethoxyresorufin showed a stimulation of 7-ethoxyresorufin-O-deethylation in the mixed reconstituted system, demonstrating that the high-affinity 2B4-1A2-reductase complex was functionally active and not merely an inhibitory complex.

Animals↗
PubMed1995

Enzymatic characterization of immunopurified prohormone convertase 2: potent inhibition by a 7B2 peptide fragment.

Prohormone convertase (PCs) are thought to mediate the controlled proteolysis of prohormones and neuropeptide precursors. While recombinant PC1 and furin are currently available, thus far it has not been possible to produce recombinant PC2. We have used conditioned medium obtained from the mouse insulinoma cell line beta TC3 to generate a working preparation of enzymatically active PC2 through immunopurification. Immunopurified PC2 cleaved the fluorogenic substrate Cbz-Arg-Ser-Lys-Arg-AMC in a time- and calcium-dependent manner. It was half-maximally stimulated at 75 microM Ca2+, had an optimum pH of 5, and exhibited PCMS and EDTA sensitivity similar to that reported for furin and PC1. The tight-binding inhibitor 27 kDa 7B2 was used to calculate the Kd for this inhibitor and the active enzyme concentration. The Kd was 7.3 +/- 1.7 nM, and the turnover rate of PC2 was 5.2 molecules substrate per enzyme molecule per minute. The specific activity was 4.9 nmol/micrograms/h (assuming a molecular mass for PC2 of 64 kDa). The enzyme preparation was able to cleave recombinant proenkephalin at at least four of the expected paired basic sites in the absence, but not in the presence, of 27 kDa 7B2. Since 21 kDa 7B2 is functionally inactive as a proteinase inhibitor, we examined the inhibitory activity of the carboxy-terminal portion of 27 kDa 7B2 (7B2 CT-peptide). Synthetic peptides were used to demonstrate that the 7B2 CT-peptide (a) represents a potent inhibitor of PC2 (Ki = 57 nM), (b) can block the conversion of proPC2 to PC2, and (c) can block the PC2-mediated conversion of proenkephalin to smaller peptide fragments.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Substrate-dependent competition of different P450 isozymes for limiting NADPH-cytochrome P450 reductase.

The goal of these studies was to demonstrate that one P450 isozyme can influence the function of another isozyme when combined in a reconstituted system. Benzphetamine and 7-pentoxyresorufin were both shown to be preferred substrates for P450 2B4 (LM2) as compared to P450 1A2 (LM4). However, these substrates exhibited different characteristics when examined in reconstituted systems containing reductase and both P450 isozymes. Whereas benzphetamine demethylation showed a small increase in catalytic activity when both P450 1A2 and 2B4 were present over the activities obtained in simple reconstituted systems, 7-pentoxyresorufin O-dealkylation (PROD) was dramatically inhibited when both isozymes were present. These results indicate that the functional interactions between P450s in complex reconstituted systems are dependent on the substrate present. Inhibition of PROD was also dependent on reductase levels, with the inhibitory effect being more pronounced at subsaturating reductase. Finally, these protein-protein interactions were shown to be dependent on the reductase concentration in the reconstituted system rather the P450 concentration, supporting the view that P450 1A2 is inhibiting the reaction by competing with P450 2B4 for reductase molecules.

Animals↗
PubMed1992

Resonance Raman studies of Rieske-type proteins.

Resonance Raman (RR) spectra are reported for the [2Fe-2S] Rieske protein from Thermus thermophilus (TRP) and phthalate dioxygenase from Pseudomonas cepacia (PDO) as a function of pH and excitation wavelength. Depolarization ratio measurements are presented for the RR spectra of spinach ferredoxin (SFD), TRP, and PDO at 74 K. By comparison with previously published RR spectra of SFD, we suggest reasonable assignments for the spectra of TRP and PDO. The spectra of PDO exhibit virtually no pH dependence, while significant changes are observed in TRP spectra upon raising the pH from 7.3 to 10.1. One band near 270 cm-1, which consists of components at 266 cm-1 and 274 cm-1, is attributed to Fe(III)-N(His) stretching motions. We suggest that these two components arise from conformers having a protonated-hydrogen-bonded imidazole (266 cm-1) and deprotonated-hydrogen-bonded imidazolate (274 cm-1) coordinated to the Fe/S cluster and that the relative populations of the two species are pH-dependent; a simple structural model is proposed to account for this behavior in the respiratory-type Rieske proteins. In addition, we have identified RR peaks associated with the bridging and terminal sulfur atoms of the Fe-S-N cluster. The RR excitation profiles of peaks associated with these atoms are indistinguishable from each other in TRP (pH 7.3) and PDO and differ greatly from those of [2Fe-2S] ferrodoxins. The profiles are bimodal with maxima near 490 nm and > approx. 550 nm. By contrast, bands associated with the Fe-N stretch show a somewhat different enhancement profile. Upon reduction, RR peaks assigned to Fe-N vibrations are no longer observed, with the resulting spectrum being remarkably similar to that reported for reduced adrenodoxin. This indicates that only modes associated with Fe-S bonds are observed and supports the idea that the reducing electron resides on the iron atom coordinated to the two histidine residues. Taken as a whole, the data are consistent with an St2FeSb2Fe[N(His)]t2 structure for the Rieske-type cluster.

Burkholderia cepacia↗
PubMed1992

Phthalate dioxygenase reductase: a modular structure for electron transfer from pyridine nucleotides to [2Fe-2S].

Phthalate dioxygenase reductase (PDR) is a prototypical iron-sulfur flavoprotein (36 kilodaltons) that utilizes flavin mononucleotide (FMN) to mediate electron transfer from the two-electron donor, reduced nicotinamide adenine nucleotide (NADH), to the one-electron acceptor, [2Fe-2S]. The crystal structure of oxidized PDR from Pseudomonas cepacia has been analyzed at 2.0 angstrom resolution resolution; reduced PDR and pyridine nucleotide complexes have been analyzed at 2.7 angstrom resolution. NADH, FMN, and the [2Fe-2S] cluster, bound to distinct domains, are brought together near a central cleft in the molecule, with only 4.9 angstroms separating the flavin 8-methyl and a cysteine sulfur ligated to iron. The domains that bind FMN and [2Fe-2S] are packed so that the flavin ring and the plane of the [2Fe-2S] core are approximately perpendicular. The [2Fe-2S] group is bound by four cysteines in a site resembling that in plant ferredoxins, but its redox potential (-174 millivolts at pH 7.0) is much higher than the potentials of plant ferredoxins. Structural and sequence similarities assign PDR to a distinct family of flavoprotein reductases, all related to ferredoxin NADP(+)-reductase.

Amino Acid Sequence↗
PubMed1989

X-ray absorption spectroscopy of the [2Fe-2S] Rieske cluster in Pseudomonas cepacia phthalate dioxygenase. Determination of core dimensions and iron ligation.

We have employed X-ray absorption spectroscopy to obtain structural information about the Rieske Fe/S center in the phthalate dioxygenase (PDO) from Pseudomonas cepacia. Native PDO contains a dinuclear Rieske Fe/S center and an additional mononuclear Fe site. In order to study selectively the Fe/S cluster, we measured data for samples in which the mononuclear site was either depleted of metal or reconstituted with Co or Zn. Our results demonstrate that the iron environment in the Rieske cluster is structurally indistinguishable from that found in other Fe/S clusters, thus strongly supporting the suggestion that the unusually high reduction potentials for Rieske clusters are due to electrostatic rather than structural effects. The average Fe-Fe distance is 2.68 (3) A for both oxidized and reduced Rieske clusters. The average Fe-S distance is 2.24 (2) A in the oxidized cluster and 2.28 (2) A in the reduced cluster. Careful analysis of the EXAFS Debye-Waller factors suggests that the bridging and terminal Fe-S distances for the oxidized cluster are 2.20 and 2.31 A, respectively. Taken together with recent ENDOR results, these studies provide a detailed structural model for the Rieske [2Fe-2S] centers.

Fourier Analysis↗
PubMed1989

Electron-nuclear double resonance spectroscopy of 15N-enriched phthalate dioxygenase from Pseudomonas cepacia proves that two histidines are coordinated to the [2Fe-2S] Rieske-type clusters.

We have performed ENDOR spectroscopy at microwave frequencies of 9 and 35 GHz at 2 K on the reduced Rieske-type [2Fe-2S] cluster of phthalate dioxygenase (PDO) from Pseudomonas cepacia. Four samples have been examined: (1) 14N (natural abundance); (2) uniformly 15N labeled; (3) [15N]histidine in a 14N background; (4) [14N]histidine in a 15N background. These studies establish unambiguously that two of the ligands to the Rieske [2Fe-2S] center are nitrogens from histidine residues. This contrasts with classical ferredoxin-type [2Fe-2S] centers in which all ligation is by sulfur of cysteine residues. Analysis of the polycrystalline ENDOR patterns has permitted us to determine for each nitrogen ligand the principal values of the hyperfine tensor and its orientation with respect to the g tensor, as well as the 14N quadrupole coupling tensor. The combination of these results with earlier Mössbauer and resonance Raman studies supports a model for the reduced cluster with both histidyl ligands bound to the ferrous ion of the spin-coupled [Fe2+ (S = 2), Fe3+ (S = 5/2)] pair. The analyses of 15N hyperfine and 14N quadrupole coupling tensors indicate that the geometry of ligation at Fe2+ is approximately tetrahedral, with the (Fe)2(N)2 plane corresponding to the g1-g3 plane, and that the planes of the histidyl imidazoles lie near that plane, although they could not both lie in the plane. The bonding parameters of the coordinated nitrogens are fully consistent with those of an spn hybrid on a histidyl nitrogen coordinated to Fe. Differences in 14N ENDOR line width provide evidence for different mobilities of the two imidazoles when the protein is in fluid solution. We conclude that the structure deduced here for the PDO cluster is generally applicable to the full class of Rieske-type centers.

Electron Transport Complex III↗
PubMed1987

Purification and characterization of phthalate oxygenase and phthalate oxygenase reductase from Pseudomonas cepacia.

An enzymatic system has been isolated that catalyzes dihydroxylation of phthalate to form 1,2-dihydroxy-4,5-dicarboxy-3,5-cyclohexadiene with consumption of NADH and O2. This system is comprised of two proteins: a flavo-iron-sulfur protein with NADH-dependent oxidoreductase activity and a nonheme iron protein with oxygenase activity. Phthalate oxygenase is a large (approximately 217 kDa) protein composed of apparently identical 48-kDa monomers. The active enzyme has one Rieske-type [2Fe-2S] center and one mononuclear iron/monomer. Removal of the mononuclear iron by incubation with EDTA or with o-phenanthroline inhibits oxygenation; ferrous ion completely restores activity. No other metals are effective. Phthalate oxygenase is specific for phthalate or other closely related compounds. However, only phthalate is tightly coupled to NADH oxidation and O2 consumption with a stoichiometry of 1:1:1. Phthalate oxygenase is chemically competent to oxygenate phthalate when artificially supplied with reducing equivalents and O2. Phthalate oxygenase reductase is required, however, for efficient catalytic activity. The reductase is a monomeric 34-kDa flavo-iron-sulfur protein containing FMN and a plant-ferredoxin-type [2Fe-2S] center in a 1:1 ratio. Phthalate oxygenase reductase is specific for NADH but can pass electrons to a variety of acceptors, including: phthalate oxygenase, cytochrome c, ferricyanide, and dichlorophenolindophenol. This system is similar to other bacterial oxygenase systems involved in aromatic degradation including: benzoate dioxygenase, toluene dioxygenase, benzene dioxygenase, and 4-methoxybenzoate demethoxylase. However, phthalate oxygenase can be isolated in large quantities and is more stable than most other such systems.

Amino Acids↗
PubMed1986

Association of ferredoxin-NADP+ reductase with NADP(H) specificity and oxidation-reduction properties.

The equilibrium properties of the NADP+ binding site of ferredoxin-NADP+ reductase (FNR, or Fd-NADP+ reductase) were examined with regard to specificity in binding, and with regard to the oxidation-reduction properties of the FNR.NADP+ complex. With the exception of 3'-NADP+, only adenosine nucleotides with a 2'-adenosyl phosphate bound to Fd-NADP+ reductase. Kd values increased in the order: 2',5'-ADP greater than 2',5'-ATP ribose greater than NADP+ greater than 2'-AMP greater than 3'-NADP+. No evidence was found for binding of NAD, NMN, or 5'-ADP. Thus the 2'-adenosylphosphate controls specificity in substrate binding, as well as specificity in enzyme activity. The low affinity of Fd-NADP+ reductase for 2'-AMP suggests that the phosphate(s) of the pyrophosphate bridge of NADP+ may also contribute significantly to binding energy. Fd-NADP+ reductase was found to form a high-affinity two-electron reduced complex (FNR.NADPH) with a NADPH; complex formation was associated with appearance of long-wavelength charge-transfer bands. Kd of FNR.NADPH complex was about 6% the Kd of oxidized FNR.NADP+ complex. As predicted by the lower Kd, the Em for reduction of FNR.NADP+ complex to the charge-transfer complex was about 40 mV more positive than the potential of the NADP+/NADPH couple. Rapid kinetic studies supported description of the charge-transfer complex as primarily oxidized FNR.NADPH. Thus, complex formation helps drive electron transfer from the flavoprotein to NADP+.

Adenine Nucleotides↗
PubMed1985

Crystallographic characterization of phthalate oxygenase reductase, an iron-sulfur flavoprotein from Pseudomonas cepacia.

Pseudomonads grown on phthalate synthesize a series of enzymes that metabolize this aromatic substrate. Among the inducible enzymes is a reductase which transfers electrons from NADH to the terminal dioxygenase that converts phthalate to the corresponding cis-1,2-dihydrodiol (Keyser, P. (1976) Ph. D. thesis, University of Miami; Ribbons, D. W., and Evans, W. C. (1960) Biochem. J. 76, 310-318). The phthalate oxygenase reductase induced in Pseudomonas cepacia is a single polypeptide chain (Mr approximately equal to 33,000) with two prosthetic groups, FMN and [2Fe-2S]. This oxidoreductase has been crystallized at pH 6.7 from polyethylene glycol 6000 in space group R3 with a = b = 113.4 A and c = 77.7 A (hexagonal indexing).

Crystallization↗
PubMed1984

Electron transfer by ferredoxin:NADP+ reductase. Rapid-reaction evidence for participation of a ternary complex.

Rapid reaction studies presented herein show that ferredoxin:NADP+ oxidoreductase (FNR, EC 1.18.1.2) catalyzes electron transfer from spinach ferredoxin (Fd) to NADP+ via a ternary complex, Fd X FNR X NADP+. In the absence of NADP+, reduction of ferredoxin:NADP+ reductase by Fd was much slower than the catalytic rate: 37-80 s-1 versus at least 445 e-s-1; dissociation of oxidized spinach ferredoxin (Fdox) from one-electron reduced ferredoxin:NADP+ reductase (FNRsq) limited the reduction of FNR. This confirms the steady-state kinetic analysis of Masaki et al. (Masaki, R., Yoshikaya, S., and Matsubara, H. (1982) Biochim. Biophys. Acta 700, 101-109). Occupation of the NADP+ binding site of FNR by NADP+ or by 2',5'-ADP (a nonreducible NADP+ analogue) greatly increased the rate of electron transfer from Fd to FNR, releiving inhibition by Fdox. NADP+ (and 2',5'-ADP) probably facilitate the dissociation of Fdox; equilibrium studies have shown that nucleotide binding decreases the association of Fd with FNR (Batie, C. J. (1983) Ph.D. dissertation, Duke University; Batie, C. J., and Kamin, H. (1982) in Flavins and Flavoproteins VII (Massey, V., and Williams, C. H., Jr., eds) pp. 679-683, Elsevier, New York; Batie, C.J., and Kamin, H. (1982) Fed. Proc. 41, 888; and Batie, C.J., and Kamin, H. (1984) J. Biol. Chem. 259, 8832-8839). Premixing Fd with FNR was found to inhibit the reaction of the flavoprotein with NADP+ and with NADPH; thus, substrate binding may be ordered, NADP+ first, then Fd. FNRred and NADP+ very rapidly formed an FNRred X NADP+ complex with flavin to nicotinamide charge transfer bands. The Fdred X NADP+ complex then relaxed to an equilibrium species; the spectrum indicated a predominance of FNRox X NADPH charge-transfer complex. However, charge-transfer species were not observed during turnover; thus, their participation in catalysis of electron transfer from Fd to NADP+ remains uncertain. The catalytic rate of Fd to NADP+ electron transfer, as well as the rates of electron transfer from Fd to FNR, and from FNR to NADP+ were decreased when the reactants were in D2O; diaphorase activity was unaffected by solvent. On the basis of the data presented, a scheme for the catalytic mechanism of catalysis by FNR is presented.

Adenosine Diphosphate↗
PubMed1984

Ferredoxin:NADP+ oxidoreductase. Equilibria in binary and ternary complexes with NADP+ and ferredoxin.

Ferredoxin:NADP+ oxidoreductase (ferredoxin: NADP+ reductase, EC 1.18.1.2) was shown to form a ternary complex with its substrates ferredoxin (Fd) and NADP(H), but the ternary complex was less stable than the separate binary complexes. Kd for oxidized binary Fd-ferredoxin NADP+ reductase complex was less than 50 nM; Kd(Fd) increased with NADP+ concentration, approaching 0.5-0.6 microM when the flavoprotein was saturated with NADP+ K(NADP+) also increased from about 14 microM to about 310 microM, on addition of excess Fd. The changes in Kd were consistent with negative cooperativity between the associations of Fd and NADP+ and with our unpublished observations which suggest that product dissociation is rate-limiting in the reaction mechanism. Similar interference in binding was observed in more reduced states; NADPH released much ferredoxin:NADP+ reductase from Fd-Sepharose whether the proteins were initially oxidized or reduced. Complexation between Fd and ferredoxin: NADP+ reductase was found to shield each center from paramagnetic probes; charge specificity suggested that the active sites of Fd and ferredoxin:NADP+ reductase were, respectively, negatively and positively charged.

Binding Sites↗
PubMed1981

The relation of pH and oxidation-reduction potential to the association state of the ferredoxin . ferredoxin:NADP+ reductase complex.

The interaction between spinach ferredoxin and ferredoxin:NADP+ reductase was studied by varying pH and oxidation-reduction state. The Kd of the oxidized ferredoxin . ferredoxin:NADP+ reductase complex increases with increasing pH in the range from pH 6 to pH 8; the Kd is pH-independent above pH 9. These data are interpreted as showing 1 proton binding/complex at neutral pH. The extent of association of the complex was also varied by manipulation of salt concentration, was also varied by manipulation of salt concentration, and of concentration of the individual proteins. Increased association accompanied a negative shift in potential of ferredoxin relative to that of ferredoxin: NADP+ reductase. Oxidation-reduction titrations showed that the oxidation-reduction potential of ferredoxin is reduced to above -510 mV when in complex with ferredoxin:NADP+ reductase, a change of about -90 mV; the potential of ferredoxin:NADP+ reductase is changed little (no more than +20 mV). Conversely, these data also showed that the oxidation-reduction state of ferredoxin strongly affected its association with the flavoprotein, increasing the Kd at least 30-fold on reduction of ferredoxin.

Ferredoxin-NADP Reductase↗