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Brand SE, Scharlau M, Geren L, Hendrix M, Parson C, Elmendorf T, Neel E, Pianalto K, Silva-Nash J, Durham B, Millett F. Accelerated Evolution of Cytochrome c in Higher Primates, and Regulation of the Reaction between Cytochrome c and Cytochrome Oxidase by Phosphorylation. Cells 2022; 11:cells11244014. [PMID: 36552779 PMCID: PMC9777161 DOI: 10.3390/cells11244014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 11/24/2022] [Accepted: 12/01/2022] [Indexed: 12/14/2022] Open
Abstract
Cytochrome c (Cc) underwent accelerated evolution from the stem of the anthropoid primates to humans. Of the 11 amino acid changes that occurred from horse Cc to human Cc, five were at Cc residues near the binding site of the Cc:CcO complex. Single-point mutants of horse and human Cc were made at each of these positions. The Cc:CcO dissociation constant KD of the horse mutants decreased in the order: T89E > native horse Cc > V11I Cc > Q12M > D50A > A83V > native human. The largest effect was observed for the mutants at residue 50, where the horse Cc D50A mutant decreased KD from 28.4 to 11.8 μM, and the human Cc A50D increased KD from 4.7 to 15.7 μM. To investigate the role of Cc phosphorylation in regulating the reaction with CcO, phosphomimetic human Cc mutants were prepared. The Cc T28E, S47E, and Y48E mutants increased the dissociation rate constant kd, decreased the formation rate constant kf, and increased the equilibrium dissociation constant KD of the Cc:CcO complex. These studies indicate that phosphorylation of these residues plays an important role in regulating mitochondrial electron transport and membrane potential ΔΨ.
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Affiliation(s)
| | - Martha Scharlau
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Lois Geren
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Marissa Hendrix
- Independent Researcher, P.O. Box 603, Dardanelle, AR 72834, USA
| | - Clayre Parson
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Tyler Elmendorf
- School of Medicine, University of Kansas Medical Center, 2060 W 39th Ave, Kansas City, KS 66103, USA
| | - Earl Neel
- Tulsa Bone and Joint Associates, Tulsa, OK 74146, USA
| | - Kaila Pianalto
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | | | - Bill Durham
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Francis Millett
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
- Correspondence:
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Scharlau M, Geren L, Zhen EY, Ma L, Rajagukguk R, Ferguson-Miller S, Durham B, Millett F. Definition of the Interaction Domain and Electron Transfer Route between Cytochrome c and Cytochrome Oxidase. Biochemistry 2019; 58:4125-4135. [PMID: 31532642 DOI: 10.1021/acs.biochem.9b00646] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The reaction between cytochrome c (Cc) and cytochrome c oxidase (CcO) was studied using horse cytochrome c derivatives labeled with ruthenium trisbipyridine at Cys 39 (Ru-39-Cc). Flash photolysis of a 1:1 complex between Ru-39-Cc and bovine CcO at a low ionic strength resulted in the electron transfer from photoreduced heme c to CuA with an intracomplex rate constant of k3 = 6 × 104 s-1. The K13A, K72A, K86A, and K87A Ru-39-Cc mutants had nearly the same k3 value but bound much more weakly to bovine CcO than wild-type Ru-39-Cc, indicating that lysines 13, 72, 86, and 87 were involved in electrostatic binding to CcO, but were not involved in the electron transfer pathway. The Rhodobacter sphaeroides (Rs) W143F mutant (bovine W104) caused a 450-fold decrease in k3 but did not affect the binding strength with CcO or the redox potential of CuA. These results are consistent with a computational model for Cc-CcO (Roberts and Pique ( 1999 ) J. Biol. Chem. 274 , 38051 - 38060 ) with the following electron transfer pathway: heme c → CcO-W104 → CcO-M207 → CuA. A crystal structure for the Cc-CcO complex with the proposed electron transfer pathway heme c → Cc-C14 → Cc-K13 → CcO-Y105 → CcO-M207 → CuA ( S. Shimada ( 2017 ) EMBO J. 36 , 291 - 300 ) is not consistent with the kinetic results because the K13A mutation had no effect on k3. Addition of 40% ethylene glycol (as present during the crystal preparation) decreased k3 significantly, indicating that it affected the conformation of the complex. This may explain the discrepancy between the current results and the crystallographic structure.
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Affiliation(s)
- Martha Scharlau
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Lois Geren
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Eugene Y Zhen
- Department of Biochemistry and Molecular Biology , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Ling Ma
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Ray Rajagukguk
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Shelagh Ferguson-Miller
- Department of Biochemistry and Molecular Biology , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Bill Durham
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Francis Millett
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
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Da Costa G, Mouret L, Chevance S, Le Rumeur E, Bondon A. NMR of molecules interacting with lipids in small unilamellar vesicles. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2007; 36:933-42. [PMID: 17565495 DOI: 10.1007/s00249-007-0186-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Revised: 05/03/2007] [Accepted: 05/07/2007] [Indexed: 11/24/2022]
Abstract
Detailed characterization of protein, peptide or drug interactions with natural membrane is still a challenge. This review focuses on the use of nuclear magnetic resonance (NMR) for the analysis of interaction of molecules with small unilamellar vesicles (SUV). These phospholipid vesicles are often used as model membranes for fluorescence or circular dichroism experiments. The various NMR approaches for studying molecule-lipid association are reviewed. After a brief survey of the SUV characterization, the use of heteronuclear NMR (phosphorous, carbon, fluorine) is described. Applications of proton NMR through transferred nuclear Overhauser effect to perform structural determination of peptide are presented. Special care is finally given to the influence of the kinetic of the interactions for the proton NMR of bound molecules in SUV, which can constitute a good model for the study of dynamical processes at the membrane surface.
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Affiliation(s)
- Grégory Da Costa
- RMN-Interactions Lipides Protéines, UMR CNRS 6026, IFR 140, PRISM, Université de Rennes 1, 35043, Rennes Cedex, France
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Wang K, Zhen Y, Sadoski R, Grinnell S, Geren L, Ferguson-Miller S, Durham B, Millett F. Definition of the interaction domain for cytochrome c on cytochrome c oxidase. Ii. Rapid kinetic analysis of electron transfer from cytochrome c to Rhodobacter sphaeroides cytochrome oxidase surface mutants. J Biol Chem 1999; 274:38042-50. [PMID: 10608873 DOI: 10.1074/jbc.274.53.38042] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The reaction between cytochrome c (Cc) and Rhodobacter sphaeroides cytochrome c oxidase (CcO) was studied using a cytochrome c derivative labeled with ruthenium trisbipyridine at lysine 55 (Ru-55-Cc). Flash photolysis of a 1:1 complex between Ru-55-Cc and CcO at low ionic strength results in electron transfer from photoreduced heme c to Cu(A) with an intracomplex rate constant of k(a) = 4 x 10(4) s(-1), followed by electron transfer from Cu(A) to heme a with a rate constant of k(b) = 9 x 10(4) s(-1). The effects of CcO surface mutations on the kinetics follow the order D214N > E157Q > E148Q > D195N > D151N/E152Q approximately D188N/E189Q approximately wild type, indicating that the acidic residues Asp(214), Glu(157), Glu(148), and Asp(195) on subunit II interact electrostatically with the lysines surrounding the heme crevice of Cc. Mutating the highly conserved tryptophan residue, Trp(143), to Phe or Ala decreased the intracomplex electron transfer rate constant k(a) by 450- and 1200-fold, respectively, without affecting the dissociation constant K(D). It therefore appears that the indole ring of Trp(143) mediates electron transfer from the heme group of Cc to Cu(A). These results are consistent with steady-state kinetic results (Zhen, Y., Hoganson, C. W., Babcock, G. T., and Ferguson-Miller, S. (1999) J. Biol. Chem. 274, 38032-38041) and a computational docking analysis (Roberts, V. A., and Pique, M. E. (1999) J. Biol. Chem. 274, 38051-38060).
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Affiliation(s)
- K Wang
- Department of Chemistry, University of Arkansas, Fayetteville, Arkansas 72701, USA
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Hazzard JT, Mauk AG, Tollin G. Laser flash photolysis studies of electron transfer mechanisms in cytochromes: an aromatic residue at position 82 is not required for cytochrome c reduction by flavin semiquinones or electron transfer from cytochrome c to cytochrome oxidase. Arch Biochem Biophys 1992; 298:91-5. [PMID: 1326255 DOI: 10.1016/0003-9861(92)90098-h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The influence of an aromatic side chain at position 82 of yeast iso-1-cytochrome c on the kinetics of its electron transfer reactions has been investigated using laser flash photolysis methods to compare a series of site-specific mutant cytochromes in their reduction by free flavin semiquinone and in electron transfer from reduced cytochrome to bovine cytochrome c oxidase. Although small (approximately 10%) but significant differences are observed between some of the mutants (S82, Y82, I82) and wild-type (F82) or G82 cytochrome in the second-order rate constant for reduction by lumiflavin semiquinone, these do not correlate with side-chain aromaticity. In the reaction between the ferrocytochromes and cytochrome c oxidase, significantly larger deviations from exponentiality are found for those mutants having aliphatic residues at position 82 than for wild type or Y82. We interpret the nonexponential behavior in terms of multiple orientations of the cytochromes within the oxidase binding site; the extent to which this occurs is apparently influenced by the character of the residue at position 82. However, a comparison of the average rate constants for electron transfer to cytochrome oxidase for the various mutants reveals that all are closely comparable to WT, except for I82 which is significantly slower (approximately threefold). These results, combined with those obtained previously from steady-state kinetic and thermodynamic measurements, suggest that the observed differences among the mutants are due to alterations in the mode of binding of the cytochrome to the oxidase, rather than to a specific requirement for the presence of an aromatic group at position 82.
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Affiliation(s)
- J T Hazzard
- Department of Biochemistry, University of Arizona, Tucson 85721
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6
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MOJARRO-GUERRA SANDRAH, AMADÒ RENATO, ARRIGONI EVI, SOLMS JUERG. Isolation of Low-Molecular-Weight Taste Peptides from Vacherin Mont Or Cheese. J Food Sci 1991. [DOI: 10.1111/j.1365-2621.1991.tb14611.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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7
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Kossekova G, Atanasov B, Bolli R, Azzi A. Ionic-strength-dependence of the oxidation of native and pyridoxal 5'-phosphate-modified cytochromes c by cytochrome c oxidase. Biochem J 1989; 262:591-6. [PMID: 2553004 PMCID: PMC1133309 DOI: 10.1042/bj2620591] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The ionic-strength-dependences of the rate constants (log k plotted versus square root of 1) for oxidation of native and pyridoxal 5'-phosphate-modified cytochromes c by three different preparations of cytochrome c oxidase have complex non-linear character, which may be explained on the basis of present knowledge of the structure of the oxidase and the monomer-dimer equilibrium of the enzyme. The wave-type curve (with a minimum and a maximum) for oxidation of native cytochrome c by purified cytochrome c oxidase depleted of phospholipids may reflect consecutively inhibition of oxidase monomers (initial descending part), competition between this inhibition and dimer formation, resulting in increased activity (second part with positive slope), and finally inhibition of oxidase dimers (last descending part of the curve). The dependence of oxidation of native cytochrome c by cytochrome c oxidase reconstituted into phospholipid vesicles is a curve with a maximum, without the initial descending part described above. This may reflect the lack of pure monomers in the vesicles, where equilibrium is shifted to dimers even at low ionic strength. Subunit-III-depleted cytochrome c oxidase does not exhibit the maximum seen with the other two enzyme preparations. This may mean that removal of subunit III hinders dimer formation. The charge interactions of each of the cytochromes c (native or modified) with the three cytochrome c oxidase preparations are similar, as judged by the similar slopes of the linear dependences at I values above the optimal one. This shows that subunit III and the phospholipid membrane do not seem to be involved in the specific charge interaction of cytochrome c oxidase with cytochrome c.
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Affiliation(s)
- G Kossekova
- Department of Chemistry and Biochemistry, Medical Academy, Sofia, Bulgaria
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8
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Armstrong GD, Chapman SK, Sisley MJ, Sykes AG, Aitken A, Osheroff N, Margoliash E. Preferred sites on cytochrome c for electron transfer with two positively charged blue copper proteins, Anabaena variabilis plastocyanin and stellacyanin. Biochemistry 1986; 25:6947-51. [PMID: 3026438 DOI: 10.1021/bi00370a031] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Rate constants for the reactions of horse cytochrome c (E'0 of +260 mV) with the copper proteins Anabaena variabilis plastocyanin (E'0 of +360 mV) used as oxidant and stellacyanin (E'0 of +187 mV) used as reductant have been determined at 25 degrees C, pH 7.5 and 7.0, respectively, and an ionic strength of 0.10 M (NaCl). These rate constants were also measured with eight different singly substituted 4-carboxy-2,6-dinitrophenyl (CDNP) horse cytochrome c derivatives, modified at lysine-7, -13, -25, -27, -60, -72, -86, or -87 and with the trinitrophenyl (TNP) derivative modified at lysine-13. The influence of the modifications on the bimolecular rate constants for these reactions defines the region on the protein that is involved in the electron-exchange reactions and demonstrates that the preferred site is at or near the solvent-accessible edge of the heme prosthetic group on the "front" surface of the molecule. Both reactions are strongly influenced by the lysine-72 modification to the left of the exposed heme edge and, to this extent, behave similar to the earlier studied reaction with azurin. These effects span only an order of magnitude in rate constants and are thus many times smaller than those for the physiological protein redox partners of cytochrome c. While the preferred sites of reaction on the surface of cytochrome c for small inorganic complexes appear to be dependent only on the net charge of the reactants, with the copper proteins additional factors intervene. These influences are discussed in terms of hydrophobic patches and the distribution of charges on the surface of the four copper proteins so far examined.
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9
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Sinjorgo KM, Steinebach OM, Dekker HL, Muijsers AO. The effects of pH and ionic strength on cytochrome c oxidase steady-state kinetics reveal a catalytic and a non-catalytic interaction domain for cytochrome c. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 850:108-15. [PMID: 3011088 DOI: 10.1016/0005-2728(86)90014-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The influence of pH and ionic strength on the steady-state kinetics of purified bovine cytochrome c oxidase was studied by spectrophotometry. At low ionic strength, increasing the pH in the range between 5.4 and 8.6 resulted in a slight decrease in maximal turnover numbers of the high-affinity and the low-affinity reactions. The high-affinity Km was also found to decrease with increasing pH. The ionic-strength dependence of the steady-state kinetics of positively charged cytochrome c oxidase at pH 6.2 and that of negatively charged cytochrome c oxidase at pH 7.8 were similar; in both cases, high-affinity Km values and high-affinity and low-affinity TNmax values increased with ionic strength. The low-affinity Km was independent of both pH and ionic strength. Above I = 100 mM, no low-affinity reaction could be observed. A description of the electrostatic interactions between cytochrome c and cytochrome c oxidase, based on the overall monopoles and overall dipoles of the two proteins, could not explain our data. We propose that at I greater than or equal to 25 mM such an approximation cannot be used for electrostatic interactions between large proteins, since the assumption that all charges on the surfaces of the reacting proteins would contribute equally to the electrostatic interaction is not valid. A qualitative description of electrostatic interactions between the two cytochromes based on limited electrostatic interaction domains on the cytochrome c oxidase surface was found to be in good agreement with all our data and supports the model of Speck et al. (Speck, S.H., Dye, D. and Margoliash, E. (1984) Proc. Natl. Acad. Sci. USA 81, 347-351), who proposed one catalytic and one non-catalytic cytochrome c binding site. It is proposed that the allosteric effect of the cytochrome c at the non-catalytic site is of an electrostatic nature. At high ionic strength (occurring in vivo), this cytochrome c molecule would then no longer affect the catalytic site, resulting in the absence of the low-affinity reaction.
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Amir D, Haas E. A series of site-specific fluorescently labeled BPTI derivatives prepared by nonselective acylation and chromatographic separations. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1986; 27:7-17. [PMID: 2419267 DOI: 10.1111/j.1399-3011.1986.tb02760.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Investigation of conformational transitions and, in particular, the folding/unfolding transitions of globular proteins by means of excitation energy transfer measurements depends on the availability of protein derivatives carrying donor and acceptor probes at well-defined pairs of sites. A series of bovine pancreatic trypsin inhibitor (BPTI) derivatives, each labeled at one of the epsilon-amino groups, was prepared. This was achieved by a nonselective acylation reaction using 7-dimethyl-amino-coumarin-4-acetyl-N-hydroxysuccinimide ester (DACA-NHSIE) as a reagent yielding a mixture of products. The mixture was resolved by affinity chromatography and reversed phase high performance liquid chromatography (HPLC). Four derivatives were obtained, each carrying the probe at one of the four amino groups. Identification of site of labeling and determination of the purity of the products was achieved by HPLC-tryptic peptide mapping. The labeled derivatives are active and can undergo a reversible denaturation/renaturation cycle. The spectral characteristics of the probe make it a suitable acceptor in energy-transfer measurements. The advantage of the approach described here, namely nonselective reaction combined with efficient fractionation procedures for the preparation of site specifically labeled derivatives, is that each of the amino groups can be labeled in a simple procedure, thus allowing for a maximal number of labeling sites which cannot be achieved when site-directed reagents (e.g. specific particular protection) are used. The present method yields derivatives which are useful in energy transfer measurements for determination of intramolecular distances between labeled sites. The derivatives should be useful in the analysis of the mechanism of protein folding and the intermediate structures involved.
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Kuo LM, Davies HC, Smith L. Monoclonal antibodies to cytochrome c from Paracoccus denitrificans: effects on electron transport reactions. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 809:388-95. [PMID: 2994723 DOI: 10.1016/0005-2728(85)90189-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effect of a monoclonal antibody to a soluble cytochrome c from Paracoccus denitrificans was tested on the membrane-bound electron-transport system of this bacterium. This antibody (F3-10.2) and one previously described (F3-29.4) (Kuo, L.M., Davies, H.C. and Smith, L. (1984) Biochim. Biophys. Acta 766, 472-482) were deduced to bind to the cytochrome c in the area including amino acid residue number 23 on a loop on the side of the heme crevice. In contrast to the observations with the previously tested antibody, the present data show the second antibody to block completely the reaction of the cytochrome c with cytochrome c oxidase but not that with cytochrome c reductase. Neither antibody has an appreciable inhibitory effect on the NADH oxidase of the isolated detergent-treated membranes. The two antibodies bind in different ways, giving insight into the interaction of a soluble protein with membrane-bound enzymes. The data indicate that the reaction sites on the cytochrome c for the oxidase and reductase moieties of P. denitrificans are different. They also argue against the need for a dissociable cytochrome c comparable to that which functions on the mitochondrial inner membrane.
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Kuo LM, Davies HC, Smith L. Effects of monoclonal antibodies to bovine and Paracoccus denitrificans cytochromes c on reactions with oxidase, reductase and peroxidase. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 766:472-82. [PMID: 6205693 DOI: 10.1016/0005-2728(84)90263-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The effects of monoclonal antibodies to bovine and Paracoccus denitrificans cytochromes c (Kuo, L.M. and Davies, H.C. (1983) Mol. Immunol. 20, 827-838) in the reactions of the cytochromes c with cytochrome c oxidase, reductase and peroxidase were studied. Spectrophotometric assays were employed, under conditions where binding of cytochrome c to the enzymes appears to be rate-limiting. Less than stoichiometric amounts of antibodies to P. denitrificans cytochrome c added to the cytochrome rendered some of it nonoxidizable or nonreducible by the P. denitrificans membrane-bound electron transport system and decreased the rate constant with the remaining cytochrome c. The antibodies appear to affect both electron transport reactions (blocking effects) with the oxidase and reductase and binding effects (effects on rate constants) and to distinguish between the two. Different ratios of antibody site to cytochrome c gave different extents of blocking of the reductase as compared with the oxidase reaction. Differences were also apparent in the effect of these antibodies on the reaction of yeast peroxidase and the oxidase with the P. denitrificans cytochrome c. Antibodies to bovine and P. denitrificans cytochromes c had considerably less effect on the reactions of the bovine cytochrome with bovine oxidase and reductase. One antibody was inhibitory to the oxidase reaction with bovine cytochrome c, but not to that with the reductase. Also, an antibody which inhibited the oxidase reaction had no effect on the reaction with yeast peroxidase. The data give evidence that the interaction areas on cytochrome c for oxidase and reductase and peroxidase are not identical, although they may be nearby.
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DIXIT BSUDHAN, VANDERKOOI JANEM. Probing Structure and Motion of the Mitochondrial Cytochromes. CURRENT TOPICS IN BIOENERGETICS 1984. [DOI: 10.1016/b978-0-12-152513-2.50011-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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14
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Speck SH, Margoliash E. Characterization of the interaction of cytochrome c and mitochondrial ubiquinol-cytochrome c reductase. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43566-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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15
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Kuo LM, Davies HC. Production, isolation and characterization of monoclonal antibodies to cytochromes c of beef heart and Paracoccus denitrificans. Mol Immunol 1983; 20:827-38. [PMID: 6312296 DOI: 10.1016/0161-5890(83)90079-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Hybridoma cell lines secreting monoclonal antibodies which bind beef heart cytochrome c or Paracoccus denitrificans cytochrome c have been produced using spleen cells from BALB/c mice immunized with cytochrome c. Immunization was performed with either the native cytochrome c, succinylated hemocyanin-conjugated cytochrome c, or beef heart cytochrome c polymerized with glutaraldehyde. Of 10 such fusions, the hybridization frequency ranged from 0 to 42%. The cell fusion efficiency, the possible factors involved in the cell fusion efficiency and the frequency of antibody producing hybridomas are described. The percentage of hybridomas positive for anti-cytochrome c antibody production as screened for by radioimmunoassay or ELISA was 2%. Of the antibodies from 12 hybridoma cell lines which resulted from 10 fusions, three were specific to beef heart cytochrome c, another three were specific to P. denitrificans cytochrome c, and the remainder reacted with both cytochromes c. These groups of monoclonal antibodies react to different sets of sites on these two cytochromes c. The monoclonal antibodies from ten representative clones have been isolated and characterized by different methods.
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Geren LM, Stonehuerner J, Davis DJ, Millett F. The use of a water-soluble carbodiimide to cross-link cytochrome c to plastocyanin. BIOCHIMICA ET BIOPHYSICA ACTA 1983; 724:62-8. [PMID: 6307354 DOI: 10.1016/0005-2728(83)90025-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A water-soluble carbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, has been used to cross-link horse heart cytochrome c to spinach chloroplast plastocyanin. The complex was formed in yields up to 90% and was found to have a stoichiometry of 1 mol plastocyanin per mol cytochrome c. The cytochrome c in the complex was fully reducible by ascorbate and potassium ferrocyanide, and had a redox potential only 25 mV less than that of native cytochrome c. The complex was nearly completely inactive towards succinate-cytochrome c reductase and cytochrome c oxidase, suggesting that the heme crevice region of cytochrome c was blocked. We propose that the carbodiimide promoted the formation of amide cross-links between lysine amino groups surrounding the heme crevice of cytochrome c and complementary carboxyl groups on plastocyanin. It is of interest that the high-affinity site for cytochrome c binding on bovine heart cytochrome c oxidase has recently been found to involve a sequence of subunit II with some homology to the copper-binding sequence of plastocyanin.
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Osheroff N, Speck SH, Margoliash E, Veerman EC, Wilms J, König BW, Muijsers AO. The reaction of primate cytochromes c with cytochrome c oxidase. Analysis of the polarographic assay. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(20)81954-1] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Butler J, Chapman SK, Davies DM, Sykes AG, Speck SH, Osheroff N, Margoliash E. Preferred sites for electron transfer between cytochrome c and iron and cobalt complexes. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)32423-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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19
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Veerman EC, Wilms J, Dekker HL, Muijsers AO, van Buuren KJ, van Gelder BF, Osheroff N, Speck SH, Margoliash E. The presteady state reaction of chemically modified cytochromes c with cytochrome oxidase. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(20)81955-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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20
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Augustin MA, Chapman SK, Davies DM, Sykes AG, Speck SH, Margoliash E. Interaction of cytochrome c with the blue copper proteins, plastocyanin and azurin. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)32424-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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21
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Veerman EC, Van Leeuwen JW, Van Buuren KJ, Van Gelder BF. The reaction of cytochrome aa3 with (porphyrin) cytochrome c as studied by pulse radiolysis. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 680:134-41. [PMID: 6284217 DOI: 10.1016/0005-2728(82)90004-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
(1) Using the pulse-radiolysis and stopped-flow techniques, the reactions of iron-free (porphyrin) cytochrome c and native cytochrome c with cytochrome aa3 were investigated. The porphyrin cytochrome c anion radical (generated by reduction of porphyrin cytochrome c by the hydrated electron) can transfer its electron to cytochrome aa3. The bimolecular rate constant for this reaction is 2 x 10(7) M-1 . s-1 (5 mM potassium phosphate, 0.5% Tween 20, pH 7.0, 20 degrees C). (2) The ionic strength dependence of the cytochrome c-cytochrome aa3 interaction was measured in the ionic strength range between 40 and 120 mM. At ionic strengths below 30 mM, a cytochrome c-cytochrome aa3 complex is formed in which cytochrome c is no longer reducible by the hydrated electron. A method is described by which the contributions of electrostatic forces to the reaction rate can be determined. (3) Using the stopped-flow technique, the effect of the dielectric constant (epsilon) of the reaction medium on the reaction of cytochrome C with cytochrome aa3 was investigated. With increasing epsilon the second-order rate constant decreased.
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22
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Koppenol WH, Margoliash E. The asymmetric distribution of charges on the surface of horse cytochrome c. Functional implications. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)34740-9] [Citation(s) in RCA: 219] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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23
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Fluorescence energy transfer studies of the interaction between adrenodoxin and cytochrome c. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)68647-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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24
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Baba ML, Darga LL, Goodman M, Czelusniak J. Evolution of cytochrome C investigated by the maximum parsimony method. J Mol Evol 1981; 17:197-213. [PMID: 6267311 DOI: 10.1007/bf01732758] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Rates of evolution for cytochrome c over the past one billion years were calculated from a maximum parsimony dendrogram which approximates the phylogeny of 87 lineages. Two periods of evolutionary acceleration and deceleration apparently occurred for the cytochrome c molecule. The tempo of evolutionary change indicated by this analysis was compared to the patterns of acceleration and deceleration in the ancestry of several other proteins. The synchrony of these tempos of molecular change supports the notion that rapid genetic evolution accompanied periods of major adaptive radiations. Rates of change at different time in several structural-functional areas of cytochrome c were also investigated in order to test the Darwinian hypothesis that during periods of rapid evolution, functional sites accumulate proportionately more substitutions than areas with no known functions. Rates of change in four proposed functional groupings of sites were therefore compared to rates in areas of unknown function for several different time periods. This analysis revealed a significant increase in the rate of evolution for sites associated with the regions of cytochrome c oxidase and reductase interaction during the period between the emergence of the eutherian ancestor to the emergence of the anthropoid ancestor.
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25
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Speck S, Koppenol W, Dethmers J, Osheroff N, Margoliash E, Rajagopalan K. Definition of cytochrome c binding domains by chemical modification. Interaction of horse cytochrome c with beef sulfite oxidase and analysis of steady state kinetics. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)68976-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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26
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27
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Smith H, Ahmed A, Millett F. Electrostatic interaction of cytochrome c with cytochrome c1 and cytochrome oxidase. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)69355-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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28
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Ahmed A, Millett F. Use of specific lysine modifications to identify the site of reaction between cytochrome c and ferricyanide. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)69850-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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29
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Goodman M. Decoding the pattern of protein evolution. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1981; 38:105-64. [PMID: 6270732 DOI: 10.1016/0079-6107(81)90012-2] [Citation(s) in RCA: 124] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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30
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Webb M, Stonehuerner J, Millett F. The use of specific lysine modifications to locate the reaction site of cytochrome c with sulfite oxidase. BIOCHIMICA ET BIOPHYSICA ACTA 1980; 593:290-8. [PMID: 6263321 DOI: 10.1016/0005-2728(80)90066-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The reduction of cytochrome c by beef liver sulfite oxidase was found to be strongly inhibited by high ionic strength, indicating the importance of electrostatic interactions to the reaction. The reaction rates of sulfite oxidase with singly trifluoroacetylated or trifluoromethylphenylcarbamylated cytochrome c derivatives were studied to determine the role of individual lysines in the reaction. The reaction rate was decreased by modification of the lysines immediately surrounding the heme crevice, the decreases following the order: Lys 13 greater than Lys 25 congruent to Lys 79 approximately equal to Lys 87 greater than Lys 8 approximately equal to Lys 27 approximately equal to Lys 72. Modification of lysines 22, 55, 88, 99, and 100 had no effect on the reaction rate. These results indicate that the interaction site on cytochrome c for sulfite oxidase is at the heme crevice region, and overlaps considerable with that for cytochrome oxidase.
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31
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Smith MB, Millett F. A 19F nuclear magnetic resonance study of the interaction between cytochrome c and cytochrome c peroxidase. BIOCHIMICA ET BIOPHYSICA ACTA 1980; 626:64-72. [PMID: 6257307 DOI: 10.1016/0005-2795(80)90197-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The reaction between ferrocytochrome c and yeast cytochrome c peroxidase was studied using cytochrome c derivatives specifically trifluoroacetylated at single lysine amino groups. The only modifications that decreased the reaction rate were those of lysines immediately surrounding the heme crevice, lysines 13, 25, 79, and 87. Modification of lysines 22, 55, 88, and 99 had no effect on the reaction. The 19F chemical shifts of the cytochrome c derivatives trifluoroacetylated at lysines 13, 79, and 87 were not changed upon complex formation with cytochrome c peroxidase, indicating that no detectable conformational changes occurred. The cytochrome c trifluoroacetyl groups had the same T1 values in the paramagnetic fluorocytochrome c peroxidase complex as in the diamagnetic reduced form of the complex, indicating that they were more than 2.3 nm from the paramagnetic iron atom in cytochrome c peroxidase. This is consistent with a separation of at least 1.5-2.0 nm between the iron atom of cytochrome c and the iron atom of cytochrome c peroxidase.
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32
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Smith MB, Stonehuerner J, Ahmed AJ, Staudenmayer N, Millett F. Use of specific trifluoroacetylation of lysine residues in cytochrome c to study the reaction with cytochrome b5, cytochrome c1, and cytochrome oxidase. BIOCHIMICA ET BIOPHYSICA ACTA 1980; 592:303-13. [PMID: 6250589 DOI: 10.1016/0005-2728(80)90191-7] [Citation(s) in RCA: 70] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The preparation, purification, and characterization of four new derivatives of cytochrome c trifluoroacetylated at lysines 72, 79, 87, and 88 are reported. The redox reaction rates of these derivatives with cytochrome b5, cytochrome c1 and cytochrome oxidase indicated that the interaction domain on cytochrome c for all three proteins involves the lysines immediately surrounding the heme crevice. Modification of lysines 72, 79, 87 had a large effect on the rate of all three reactions, while modification of lysine 88 had a very small effect. Even though lysines 87 and 88 are adjacent to one another, lysine 87 is at the top left of the heme crevice oriented towards the front of cytochrome c, while lysine 88 is oriented more towards the back. Since the interaction sites for cytochrome c1 and cytochrome oxidase are essentially identical, cytochrome c probably undergoes some type of rotational diffusion during electron transport.
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33
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Osheroff N, Brautigan D, Margoliash E. Definition of enzymic interaction domains on cytochrome c. Purification and activity of singly substituted carboxydinitrophenyl-lysine 7, 25, 73, 86, and 99 cytochromes c. J Biol Chem 1980. [DOI: 10.1016/s0021-9258(19)70638-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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34
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35
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Margoliash E. Evolutionary adaptation of mitochondrial cytochrome c to its functional milieu. UCLA FORUM IN MEDICAL SCIENCES 1980:299-321. [PMID: 233495 DOI: 10.1016/b978-0-12-643150-6.50024-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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36
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Yoshimura T, Matsushima A, Aki K. Interaction of cytochrome c with the phosphorprotein phosvitin. BIOCHIMICA ET BIOPHYSICA ACTA 1979; 581:316-24. [PMID: 229914 DOI: 10.1016/0005-2795(79)90251-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Candida krusei cytochrome c forms a molecular complex with phosphorprotein phosvitin in weakly alkaline solution of low ionic strength. At most, about 22 molecules of cytochrome c bind to a phosvitin molecule. The complex at the binding ratio below about 11 (half of the maximum ratio) as a much higher binding strength. Several lines of evidence indicate that the marked difference in the binding strength is due to the difference in negative charges on phosvitin molecule concerned in the binding of a cytochrome c molecule. The phosvitin-bound cytochrome c seems to have a preferred orientation with the front surface of the molecule containing the exposed heme edge in contact with the phosvitin molecule.
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37
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Site-specific anti-cytochrome c antibodies. Inhibition of the reactions between cytochrome c and its respiratory chain electron exchange partners. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(19)86372-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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38
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Taborsky G, McCollum K. Phosphate binding by cytochrome c. Specific binding site involved in the formation and reactivity of a complex of ferricytochrome c, ferrous ion, and phosphate. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(18)50285-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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39
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Smith L, Davies HC, Nava ME. Studies of the kinetics of oxidation of cytochrome c by cytochrome c oxidase: comparison of spectrophotometric and polarographic assays. Biochemistry 1979; 18:3140-6. [PMID: 37897 DOI: 10.1021/bi00581a035] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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40
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Speck SH, Ferguson-Miller S, Osheroff N, Margoliash E. Definition of cytochrome c binding domains by chemical modification: kinetics of reaction with beef mitochondrial reductase and functional organization of the respiratory chain. Proc Natl Acad Sci U S A 1979; 76:155-9. [PMID: 218193 PMCID: PMC382895 DOI: 10.1073/pnas.76.1.155] [Citation(s) in RCA: 120] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
An assay has been developed to study the steady-state kinetics of the reduction of cytochrome c by purified beef heart mitochondrial cytochrome c reductase (cytochrome bc(1) complex, complex III). An analogue of coenzyme Q(2) (2,3-dimethoxy-5-methyl-6-decylhydroquinone) was employed as an antimycin-sensitive reductant. The kinetics of reaction of ten different mono(4-carboxy-2,6-dinitrophenyl) derivatives of horse cytochrome c were determined. The modified proteins showed higher apparent K(m) values than the native protein and greater sensitivity to ionic strength, defining an interaction domain on cytochrome c for purified cytochrome c reductase. This interaction site is located on the front surface of the molecule (which contains the exposed heme edge) and surrounds the point at which the positive end of the dipole axis crosses the surface of the protein. The site is similar to that previously determined for mitochondrial cytochrome c oxidase and yeast cytochrome c peroxidase, suggesting that the primary interaction with redox partners is directed by the dipolar charge distribution on cytochrome c. The extensive overlapping of the interaction domains for the mitochondrial cytochrome c oxidase and reductase indicates that cytochrome c must be mobile in order to transfer electrons between them, depending on their relative positions in the membrane. Whether such mobility is necessary in intact mitochondria depends on whether the interactions with the complete membrane-bound system are the same as with the purified components.
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41
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Rieder R, Bosshard H. The cytochrome c oxidase binding site on cytochrome c. Differential chemical modification of lysine residues in free and oxidase-bound cytochrome c. J Biol Chem 1978. [DOI: 10.1016/s0021-9258(17)34577-5] [Citation(s) in RCA: 84] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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42
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43
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Brautigan D, Ferguson-Miller S, Margoliash E. Definition of cytochrome c binding domains by chemical modification. I. Reaction with 4-chloro-3,5-dinitrobenzoate and chromatographic separation of singly substituted derivatives. J Biol Chem 1978. [DOI: 10.1016/s0021-9258(17)38279-0] [Citation(s) in RCA: 120] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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44
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Definition of cytochrome c binding domains by chemical modification. II. Identification and properties of singly substituted carboxydinitrophenyl cytochromes c at lysines 8, 13, 22, 27, 39, 60, 72, 87, and 99. J Biol Chem 1978. [DOI: 10.1016/s0021-9258(17)38280-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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45
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Definition of cytochrome c binding domains by chemical modification. III. Kinetics of reaction of carboxydinitrophenyl cytochromes c with cytochrome c oxidase. J Biol Chem 1978. [DOI: 10.1016/s0021-9258(17)38281-9] [Citation(s) in RCA: 351] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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46
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Brautigan DL, Ferguson-Miller S, Margoliash E. Mitochondrial cytochrome c: preparation and activity of native and chemically modified cytochromes c. Methods Enzymol 1978; 53:128-64. [PMID: 213675 DOI: 10.1016/s0076-6879(78)53021-8] [Citation(s) in RCA: 313] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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47
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Critz WJ, Martinez-Carrion M. Fluorine-19 nuclear magnetic resonance studies of effects of ligands on trifluoroacetonylated supernatant aspartate transaminase. Biochemistry 1977; 16:1559-64. [PMID: 15584 DOI: 10.1021/bi00627a005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The selective reaction of Cys-45 and -82, on the one hand, and Cys-390, on the other, with 3-bromo-1,1,1-trifluoropropanone allows for the probing of these regions of aspartate transaminase in the absence and in the presence of enzymatic ligands by 19F nuclear magnetic resonance (NMR). The 19F chemical shifts of the resonance lines differ for the three cysteines and so does their behavior with pH changes. The resonance signals with chemical shifts at 615 and 800 Hz upfield from trifluoroacetic acid correspond to modified cysteine-82 and -45 and have tentatively been assigned in this order. The 615-Hz resonance is affected by pH changes that fit best the influence of a single ionizing residue. On the 800-Hz line, the pH changes appear to be the influence of a minimum of two ionizing residues. The 19F resonance from modified Cys-390 is pH independent in the pH range 5-9 for the pyridoxal phosphate, pyridoxamine phosphate, and apoenzyme forms of the enzyme. Occupation of the active site by a quasi-enzyme-substrate complex, trifluoromethionine pyridoxyl phosphate, affects the 19F chemical shift of modified Cys-390, making it pH dependent with a pK value of 8.4. The 19F NMR properties of the pyridoxal form of Cys-390-modified enzyme can be used to monitor some ligand interactions with the active-center region. Addition of alpha-ketoglutarate or succinate to the ketone labeled enzyme causes a decrease in the resonance line width, and titrations show that this procedure is a good method with which to study the affinity of the enzyme for these ligands. The interpretation of the chemical shift and line-width characteristics of the 19F resonance arising from Cys-390 are most consistent with a model in which the region around this residue seems to be affected by conformational changes arising from substrate binding to the active-center subsites in productive (covalent) manner. Nonproductive complexes which possess fast ligand-protein exchange, such as those between alpha-ketoglutarate or succinate with the pyridoxal phosphate form of the enzyme, may result only in a greater degree of freedom for Cys-390.
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