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Freeman SL, Skafar V, Kwon H, Fielding AJ, Moody PCE, Martínez A, Issoglio FM, Inchausti L, Smircich P, Zeida A, Piacenza L, Radi R, Raven EL. Crystal structure of Trypanosoma cruzi heme peroxidase and characterization of its substrate specificity and compound I intermediate. J Biol Chem 2022; 298:102204. [PMID: 35772495 PMCID: PMC9358470 DOI: 10.1016/j.jbc.2022.102204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/21/2022] [Accepted: 06/22/2022] [Indexed: 11/26/2022] Open
Abstract
The protozoan parasite Trypanosoma cruzi is the causative agent of American trypanosomiasis, otherwise known as Chagas disease. To survive in the host, the T. cruzi parasite needs antioxidant defense systems. One of these is a hybrid heme peroxidase, the T. cruzi ascorbate peroxidase-cytochrome c peroxidase enzyme (TcAPx-CcP). TcAPx-CcP has high sequence identity to members of the class I peroxidase family, notably ascorbate peroxidase (APX) and cytochrome c peroxidase (CcP), as well as a mitochondrial peroxidase from Leishmania major (LmP). The aim of this work was to solve the structure and examine the reactivity of the TcAPx-CcP enzyme. Low temperature electron paramagnetic resonance spectra support the formation of an exchange-coupled [Fe(IV)=O Trp233•+] compound I radical species, analogous to that used in CcP and LmP. We demonstrate that TcAPx-CcP is similar in overall structure to APX and CcP, but there are differences in the substrate-binding regions. Furthermore, the electron transfer pathway from cytochrome c to the heme in CcP and LmP is preserved in the TcAPx-CcP structure. Integration of steady state kinetic experiments, molecular dynamic simulations, and bioinformatic analyses indicates that TcAPx-CcP preferentially oxidizes cytochrome c but is still competent for oxidization of ascorbate. The results reveal that TcAPx-CcP is a credible cytochrome c peroxidase, which can also bind and use ascorbate in host cells, where concentrations are in the millimolar range. Thus, kinetically and functionally TcAPx-CcP can be considered a hybrid peroxidase.
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Affiliation(s)
- Samuel L Freeman
- School of Chemistry, University of Bristol, Bristol, United Kingdom
| | - Vera Skafar
- Departamento de Bioquímica, Facultad of Medicina, Universidad de la República, Montevideo, Uruguay; Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Hanna Kwon
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester, United Kingdom
| | - Alistair J Fielding
- Centre for Natural Products Discovery, School of Pharmacy and Biomolecular Sciences, Liverpool John Moore University, Liverpool, United Kingdom
| | - Peter C E Moody
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester, United Kingdom
| | - Alejandra Martínez
- Departamento de Bioquímica, Facultad of Medicina, Universidad de la República, Montevideo, Uruguay; Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Federico M Issoglio
- CONICET-Universidad de Buenos Aires, Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN), Buenos Aires, Argentina; Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB NOVA), Oeiras, Portugal
| | - Lucas Inchausti
- Laboratorio de Bioinformática, Departamento de Genómica, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay; Laboratorio de Interacciones Moleculares, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Pablo Smircich
- Laboratorio de Bioinformática, Departamento de Genómica, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay; Laboratorio de Interacciones Moleculares, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Ari Zeida
- Departamento de Bioquímica, Facultad of Medicina, Universidad de la República, Montevideo, Uruguay; Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Lucía Piacenza
- Departamento de Bioquímica, Facultad of Medicina, Universidad de la República, Montevideo, Uruguay; Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Rafael Radi
- Departamento de Bioquímica, Facultad of Medicina, Universidad de la República, Montevideo, Uruguay; Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
| | - Emma L Raven
- School of Chemistry, University of Bristol, Bristol, United Kingdom.
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Di Savino A, Foerster JM, Ullmann GM, Ubbink M. Enhancing the population of the encounter complex affects protein complex formation efficiency. FEBS J 2021; 289:535-548. [PMID: 34403572 PMCID: PMC9293183 DOI: 10.1111/febs.16159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 07/08/2021] [Accepted: 08/16/2021] [Indexed: 11/30/2022]
Abstract
Optimal charge distribution is considered to be important for efficient formation of protein complexes. Electrostatic interactions guide encounter complex formation that precedes the formation of an active protein complex. However, disturbing the optimized distribution by introduction of extra charged patches on cytochrome c peroxidase does not lead to a reduction in productive encounters with its partner cytochrome c. To test whether a complex with a high population of encounter complex is more easily affected by suboptimal charge distribution, the interactions of cytochrome c mutant R13A with wild‐type cytochrome c peroxidase and a variant with an additional negative patch were studied. The complex of the peroxidase and cytochrome c R13A was reported to have an encounter state population of 80%, compared to 30% for the wild‐type cytochrome c. NMR analysis confirms the dynamic nature of the interaction and demonstrates that the mutant cytochrome c samples the introduced negative patch. Kinetic experiments show that productive complex formation is fivefold to sevenfold slower at moderate and high ionic strength values for cytochrome c R13A but the association rate is not affected by the additional negative patch on cytochrome c peroxidase, showing that the total charge on the protein surface can compensate for less optimal charge distribution. At low ionic strength (44 mm), the association with the mutant cytochrome c reaches the same high rates as found for wild‐type cytochrome c, approaching the diffusion limit.
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Di Savino A, Foerster JM, Ullmann GM, Ubbink M. The Charge Distribution on a Protein Surface Determines Whether Productive or Futile Encounter Complexes Are Formed. Biochemistry 2021; 60:747-755. [PMID: 33646750 PMCID: PMC8041253 DOI: 10.1021/acs.biochem.1c00021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
![]()
Protein complex formation
depends strongly on electrostatic interactions.
The distribution of charges on the surface of redox proteins is often
optimized by evolution to guide recognition and binding. To test the
degree to which the electrostatic interactions between cytochrome c peroxidase (CcP) and cytochrome c (Cc)
are optimized, we produced five CcP variants, each with a different
charge distribution on the surface. Monte Carlo simulations show that
the addition of negative charges attracts Cc to the new patches, and
the neutralization of the charges in the regular, stereospecific binding
site for Cc abolishes the electrostatic interactions in that region
entirely. For CcP variants with the charges in the regular binding
site intact, additional negative patches slightly enhance productive
complex formation, despite disrupting the optimized charge distribution.
Removal of the charges in the regular binding site results in a dramatic
decrease in the complex formation rate, even in the presence of highly
negative patches elsewhere on the surface. We conclude that additional
charge patches can result in either productive or futile encounter
complexes, depending on whether negative residues are located also
in the regular binding site.
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Affiliation(s)
- Antonella Di Savino
- Leiden University, Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Johannes M Foerster
- University of Bayreuth, Computational Biochemistry, Universitätsstraße 30, NW I, 95447 Bayreuth, Germany
| | - G Matthias Ullmann
- University of Bayreuth, Computational Biochemistry, Universitätsstraße 30, NW I, 95447 Bayreuth, Germany
| | - Marcellus Ubbink
- Leiden University, Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, The Netherlands
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Di Savino A, Foerster JM, La Haye T, Blok A, Timmer M, Ullmann GM, Ubbink M. Efficient Encounter Complex Formation and Electron Transfer to Cytochrome c Peroxidase with an Additional, Distant Electrostatic Binding Site. Angew Chem Int Ed Engl 2020; 59:23239-23243. [PMID: 32827196 PMCID: PMC7756542 DOI: 10.1002/anie.202010006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Indexed: 12/14/2022]
Abstract
Electrostatic interactions can strongly increase the efficiency of protein complex formation. The charge distribution in redox proteins is often optimized to steer a redox partner to the electron transfer active binding site. To test whether the optimized distribution is more important than the strength of the electrostatic interactions, an additional negative patch was introduced on the surface of cytochrome c peroxidase, away from the stereospecific binding site, and its effect on the encounter complex as well as the rate of complex formation was determined. Monte Carlo simulations and paramagnetic relaxation enhancement NMR experiments indicate that the partner, cytochrome c, interacts with the new patch. Unexpectedly, the rate of the active complex formation was not reduced, but rather slightly increased. The findings support the idea that for efficient protein complex formation the strength of the electrostatic interaction is more critical than an optimized charge distribution.
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Affiliation(s)
- Antonella Di Savino
- Leiden UniversityInstitute of ChemistryEinsteinweg 552333 CCLeidenNetherlands
| | - Johannes M. Foerster
- University of BayreuthComputational BiochemistryUniversitätsstraße 30, NW I95447BayreuthGermany
| | - Thijmen La Haye
- Leiden UniversityInstitute of ChemistryEinsteinweg 552333 CCLeidenNetherlands
- Present address: University of DelftTNW Applied SciencesVan der Maasweg 92629 HZDelftThe Netherlands
| | - Anneloes Blok
- Leiden UniversityInstitute of ChemistryEinsteinweg 552333 CCLeidenNetherlands
| | - Monika Timmer
- Leiden UniversityInstitute of ChemistryEinsteinweg 552333 CCLeidenNetherlands
| | - G. Matthias Ullmann
- University of BayreuthComputational BiochemistryUniversitätsstraße 30, NW I95447BayreuthGermany
| | - Marcellus Ubbink
- Leiden UniversityInstitute of ChemistryEinsteinweg 552333 CCLeidenNetherlands
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5
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Di Savino A, Foerster JM, La Haye T, Blok A, Timmer M, Ullmann GM, Ubbink M. Efficient Encounter Complex Formation and Electron Transfer to Cytochrome
c
Peroxidase with an Additional, Distant Electrostatic Binding Site. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202010006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Antonella Di Savino
- Leiden University Institute of Chemistry Einsteinweg 55 2333 CC Leiden Netherlands
| | - Johannes M. Foerster
- University of Bayreuth Computational Biochemistry Universitätsstraße 30, NW I 95447 Bayreuth Germany
| | - Thijmen La Haye
- Leiden University Institute of Chemistry Einsteinweg 55 2333 CC Leiden Netherlands
- Present address: University of Delft TNW Applied Sciences Van der Maasweg 9 2629 HZ Delft The Netherlands
| | - Anneloes Blok
- Leiden University Institute of Chemistry Einsteinweg 55 2333 CC Leiden Netherlands
| | - Monika Timmer
- Leiden University Institute of Chemistry Einsteinweg 55 2333 CC Leiden Netherlands
| | - G. Matthias Ullmann
- University of Bayreuth Computational Biochemistry Universitätsstraße 30, NW I 95447 Bayreuth Germany
| | - Marcellus Ubbink
- Leiden University Institute of Chemistry Einsteinweg 55 2333 CC Leiden Netherlands
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Erman JE, Vitello LB, Pearl NM, Jacobson T, Francis M, Alberts E, Kou A, Bujarska K. Binding of Yeast Cytochrome c to Forty-Four Charge-Reversal Mutants of Yeast Cytochrome c Peroxidase: Isothermal Titration Calorimetry. Biochemistry 2015. [PMID: 26212209 DOI: 10.1021/acs.biochem.5b00686] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previously, we constructed, expressed, and purified 46 charge-reversal mutants of yeast cytochrome c peroxidase (CcP) and determined their electronic absorption spectra, their reaction with H2O2, and their steady-state catalytic properties [ Pearl , N. M. et al. (2008) Biochemistry 47 , 2766 - 2775 ]. Forty-four of the mutants involve the conversion of either an aspartate or glutamate residue to a lysine residue, while two are positive-to-negative mutations, R31E and K149D. In this paper, we report on a calorimetric study of the interaction of each charge-reversal mutant (excluding the internal mutants D76K and D235K) with recombinant yeast iso-1 ferricytochrome c(C102T) (yCc) under conditions where only one-to-one yCc/CcP complex formation is observed. Thirteen of the 44 surface-site charge-reversal mutants decrease the binding affinity for yCc by a factor of 2 or more. Eight of the 13 mutations (E32K, D33K, D34K, E35K, E118K, E201K, E290K, E291K) occur within, or on the immediate periphery, of the crystallographically defined yCc binding site [ Pelletier , H. and Kraut , J. (1992) Science 258 , 1748 - 1755 ], three of the mutations (D37K, E98K, E209K) are slightly removed from the crystallographic site, and two of the mutations (D165K, D241K) occur on the "back-side" of CcP. The current study is consistent with a model for yCc binding to CcP in which yCc binds predominantly near the region defined by crystallographic structure of the 1:1 yCc-CcP complex, whether as a stable electron-transfer active complex or as part of a dynamic encounter complex.
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Affiliation(s)
- James E Erman
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
| | - Lidia B Vitello
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
| | - Naw May Pearl
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
| | - Timothy Jacobson
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
| | - Meka Francis
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
| | - Erik Alberts
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
| | - Allen Kou
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
| | - Kathy Bujarska
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States
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7
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Chreifi G, Hollingsworth SA, Li H, Tripathi S, Arce AP, Magaña-Garcia HI, Poulos TL. Enzymatic Mechanism of Leishmania major Peroxidase and the Critical Role of Specific Ionic Interactions. Biochemistry 2015; 54:3328-36. [PMID: 25941976 DOI: 10.1021/acs.biochem.5b00338] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Leishmania major peroxidase (LmP) is very similar to the well-known yeast cytochrome c peroxidase (CcP). Both enzymes catalyze the peroxidation of cytochrome c. Like CcP, LmP reacts with H2O2 to form Compound I, which consists of a ferryl heme and a Trp radical, Fe(IV)═O;Trp(•+). Cytochrome c (Cytc) reduces the Trp radical to give Compound II, Fe(IV)═O;Trp, which is followed by an intramolecular electron transfer to give Fe(III)-OH;Trp(•+), and in the last step, Cytc reduces the Trp radical. In this study, we have used steady-state and single-turnover kinetics to improve our understanding of the overall mechanism of LmP catalysis. While the activity of CcP greatly increases with ionic strength, the kcat for LmP remains relatively constant at all ionic strengths tested. Therefore, unlike CcP, where dissociation of oxidized Cytc is limiting at low ionic strengths, association/dissociation reactions are not limiting at any ionic strength in LmP. We conclude that in LmP, the intramolecular electron transfer reaction, Fe(IV)═O;Trp to Fe(III)-OH;Trp(•+), is limiting at all ionic strengths. Unlike CcP, LmP depends on key intermolecular ion pairs to form the electron transfer competent complex. Mutating these sites causes the initial rate of association to decrease by 2 orders of magnitude and a substantial decrease in kcat. The drop in kcat is due to a switch in the rate-limiting step of the mutants from intramolecular electron transfer to the rate of association in forming the LmP-LmCytc complex. These studies show that while LmP and CcP form very similar complexes and exhibit similar activities, they substantially differ in how their activity changes as a function of ionic strength. This difference is primarily due to the heavy reliance of LmP on highly specific intermolecular ion pairs, while CcP relies mainly on nonpolar interactions.
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Affiliation(s)
- Georges Chreifi
- †Department of Molecular Biology and Biochemistry, ‡Department of Chemistry, and §Department of Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Scott A Hollingsworth
- †Department of Molecular Biology and Biochemistry, ‡Department of Chemistry, and §Department of Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Huiying Li
- †Department of Molecular Biology and Biochemistry, ‡Department of Chemistry, and §Department of Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Sarvind Tripathi
- †Department of Molecular Biology and Biochemistry, ‡Department of Chemistry, and §Department of Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Anton P Arce
- †Department of Molecular Biology and Biochemistry, ‡Department of Chemistry, and §Department of Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Hugo I Magaña-Garcia
- †Department of Molecular Biology and Biochemistry, ‡Department of Chemistry, and §Department of Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Thomas L Poulos
- †Department of Molecular Biology and Biochemistry, ‡Department of Chemistry, and §Department of Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
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8
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Bidwai AK, Meyen C, Kilheeney H, Wroblewski D, Vitello LB, Erman JE. Apolar distal pocket mutants of yeast cytochrome c peroxidase: hydrogen peroxide reactivity and cyanide binding of the TriAla, TriVal, and TriLeu variants. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1834:137-48. [PMID: 23022490 DOI: 10.1016/j.bbapap.2012.09.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 09/06/2012] [Accepted: 09/07/2012] [Indexed: 11/28/2022]
Abstract
Three yeast cytochrome c peroxidase (CcP) variants with apolar distal heme pockets have been constructed. The CcP variants have Arg48, Trp51, and His52 mutated to either all alanines, CcP(triAla), all valines, CcP(triVal), or all leucines, CcP(triLeu). The triple mutants have detectable enzymatic activity at pH 6 but the activity is less than 0.02% that of wild-type CcP. The activity loss is primarily due to the decreased rate of reaction between the triple mutants and H(2)O(2) compared to wild-type CcP. Spectroscopic properties and cyanide binding characteristics of the triple mutants have been investigated over the pH stability region of CcP, pH 4 to 8. The absorption spectra indicate that the CcP triple mutants have hemes that are predominantly five-coordinate, high-spin at pH 5 and six-coordinate, low-spin at pH 8. Cyanide binding to the triple mutants is biphasic indicating that the triple mutants have two slowly-exchanging conformational states with different cyanide affinities. The binding affinity for cyanide is reduced at least two orders of magnitude in the triple mutants compared to wild-type CcP and the rate of cyanide binding is reduced by four to five orders of magnitude. Correlation of the reaction rates of CcP and 12 distal pocket mutants with H(2)O(2) and HCN suggests that both reactions require ionization of the reactants within the distal heme pocket allowing the anion to bind the heme iron. Distal pocket features that promote substrate ionization (basic residues involved in base-catalyzed substrate ionization or polar residues that can stabilize substrate anions) increase the overall rate of reaction with H(2)O(2) and HCN while features that inhibit substrate ionization slow the reactions.
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Affiliation(s)
- Anil K Bidwai
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115, USA
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9
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Cytochrome c signalosome in mitochondria. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 40:1301-15. [DOI: 10.1007/s00249-011-0774-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 10/12/2011] [Accepted: 10/21/2011] [Indexed: 10/15/2022]
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10
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Volkov AN, Nicholls P, Worrall JA. The complex of cytochrome c and cytochrome c peroxidase: The end of the road? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1482-503. [DOI: 10.1016/j.bbabio.2011.07.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 07/21/2011] [Accepted: 07/22/2011] [Indexed: 11/25/2022]
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Lederer F. Another look at the interaction between mitochondrial cytochrome c and flavocytochrome b (2). EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 40:1283-99. [PMID: 21503671 DOI: 10.1007/s00249-011-0697-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Revised: 02/28/2011] [Accepted: 03/16/2011] [Indexed: 11/29/2022]
Abstract
Yeast flavocytochrome b (2) tranfers reducing equivalents from lactate to oxygen via cytochrome c and cytochrome c oxidase. The enzyme catalytic cycle includes FMN reduction by lactate and reoxidation by intramolecular electron transfer to heme b (2). Each subunit of the soluble tetrameric enzyme consists of an N terminal b (5)-like heme-binding domain and a C terminal flavodehydrogenase. In the crystal structure, FMN and heme are face to face, and appear to be in a suitable orientation and at a suitable distance for exchanging electrons. But in one subunit out of two, the heme domain is disordered and invisible. This raises a central question: is this mobility required for interaction with the physiological acceptor cytochrome c, which only receives electrons from the heme and not from the FMN? The present review summarizes the results of the variety of methods used over the years that shed light on the interactions between the flavin and heme domains and between the enzyme and cytochrome c. The conclusion is that one should consider the interaction between the flavin and heme domains as a transient one, and that the cytochrome c and the flavin domain docking areas on the heme b (2) domain must overlap at least in part. The heme domain mobility is an essential component of the flavocytochrome b (2) functioning. In this respect, the enzyme bears similarity to a variety of redox enzyme systems, in particular those in which a cytochrome b (5)-like domain is fused to proteins carrying other redox functions.
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Affiliation(s)
- Florence Lederer
- Laboratoire de Chimie Physique, Université Paris-Sud, Orsay Cedex, France.
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12
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Shifting the equilibrium between the encounter state and the specific form of a protein complex by interfacial point mutations. J Am Chem Soc 2010; 132:11487-95. [PMID: 20672804 DOI: 10.1021/ja100867c] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent experimental studies have confirmed a long-held view that protein complex formation proceeds via a short-lived encounter state. The population of this transient intermediate, stabilized mainly by long-range electrostatic interactions, varies among different complexes. Here we show that the occupancy of the encounter state can be modulated across a broad range by single point mutations of interfacial residues. Using a combination of Monte Carlo simulations and paramagnetic relaxation enhancement NMR spectroscopy, we illustrate that it is possible to both enhance and diminish the binding specificity in an electron transfer complex of yeast cytochrome c (Cc) and cytochrome c peroxidase. The Cc T12A mutation decreases the population of the encounter to 10% as compared with 30% in the wild-type complex. More dramatically, the Cc R13A substitution reverses the relative occupancies of the stereospecific and the encounter forms, with the latter now being the dominant species with the population of 80%. This finding indicates that the encounter state can make a large contribution to the stability of a protein complex. Also, it appears that by adjusting the amount of the encounter through a judicious choice of point mutations, we can remodel the energy landscape of a protein complex and tune its binding specificity.
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13
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Nocek JM, Knutson AK, Xiong P, Co NP, Hoffman BM. Photoinitiated singlet and triplet electron transfer across a redesigned [myoglobin, cytochrome b5] interface. J Am Chem Soc 2010; 132:6165-75. [PMID: 20392066 PMCID: PMC2868514 DOI: 10.1021/ja100499j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We describe a strategy by which reactive binding of a weakly bound, 'dynamically docked (DD)' complex without a known structure can be strengthened electrostatically through optimized placement of surface charges, and discuss its use in modulating complex formation between myoglobin (Mb) and cytochrome b(5) (b(5)). The strategy employs paired Brownian dynamics (BD) simulations, one which monitors overall binding, the other reactive binding, to examine [X --> K] mutations on the surface of the partners, with a focus on single and multiple [D/E --> K] charge reversal mutations. This procedure has been applied to the [Mb, b(5)] complex, indicating mutations of Mb residues D44, D60, and E85 to be the most promising, with combinations of these showing a nonlinear enhancement of reactive binding. A novel method of displaying BD profiles shows that the 'hits' of b(5) on the surfaces of Mb(WT), Mb(D44K/D60K), and Mb(D44K/D60K/E85K) progressively coalesce into two 'clusters': a 'diffuse' cluster of hits that are distributed over the Mb surface and have negligible electrostatic binding energy and a 'reactive' cluster of hits with considerable stability that are localized near its heme edge, with short Fe-Fe distances favorable to electron transfer (ET). Thus, binding and reactivity progressively become correlated by the mutations. This finding relates to recent proposals that complex formation is a two-step process, proceeding through the formation of a weakly bound encounter complex to a well-defined bound complex. The design procedure has been tested through measurements of photoinitiated ET between the Zn-substituted forms of Mb(WT), Mb(D44K/D60K), and Mb(D44K/D60K/E85K) and Fe(3+)b(5). Both mutants convert the complex from the DD regime exhibited by Mb(WT), in which the transient complex is in fast kinetic exchange with its partners, k(off) >> k(et), to the slow-exchange regime, k(et) >> k(off), and both mutants exhibit rapid intracomplex ET from the triplet excited state to Fe(3+)b(5) (rate constant, k(et) approximately 10(6) s(-1)). The affinity constants of the mutant Mbs cannot be derived through conventional analysis procedures because intracomplex singlet ET quenching causes the triplet-ground absorbance difference to progressively decrease during a titration, but this effect has been incorporated into a new procedure for computing binding constants. Most importantly, these measurements reveal the presence of fast photoinduced singlet ET across the protein-protein interface, (1)k(et) approximately 2 x 10(8) s(-1).
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Yadav RK, Dolai S, Pal S, Adak S. Role of C-terminal acidic cluster in stabilization of heme spin state of ascorbate peroxidase from Leishmania major. Arch Biochem Biophys 2010; 495:129-35. [DOI: 10.1016/j.abb.2010.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 01/04/2010] [Accepted: 01/05/2010] [Indexed: 10/20/2022]
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Xiong P, Nocek JM, Griffin AKK, Wang J, Hoffman BM. Electrostatic redesign of the [myoglobin, cytochrome b5] interface to create a well-defined docked complex with rapid interprotein electron transfer. J Am Chem Soc 2009; 131:6938-9. [PMID: 19419145 DOI: 10.1021/ja902131d] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cyt b(5) is the electron-carrier "repair" protein that reduces met-Mb and met-Hb to their O(2)-carrying ferroheme forms. Studies of electron transfer (ET) between Mb and cyt b(5) revealed that they react on a "Dynamic Docking" (DD) energy landscape on which binding and reactivity are uncoupled: binding is weak and involves an ensemble of nearly isoenergetic configurations, only a few of which are reactive; those few contribute negligibly to binding. We set the task of redesigning the surface of Mb so that its reaction with cyt b(5) instead would occur on a conventional "simple docking" (SD) energy landscape, on which a complex exhibits a well-defined (set of) reactive binding configuration(s), with binding and reactivity thus no longer being decoupled. We prepared a myoglobin (Mb) triple mutant (D44K/D60K/E85K; Mb(+6)) substituted with Zn-deuteroporphyrin and monitored cytochrome b(5) (cyt b(5)) binding and electron transfer (ET) quenching of the (3)ZnMb(+6) triplet state. In contrast, to Mb(WT), the three charge reversals around the "front-face" heme edge of Mb(+6) have directed cyt b(5) to a surface area of Mb adjacent to its heme, created a well-defined, most-stable structure that supports good ET pathways, and apparently coupled binding and ET: both K(a) and k(et) are increased by the same factor of approximately 2 x 10(2), creating a complex that exhibits a large ET rate constant, k(et) = 10(6 1) s(-1), and is in slow exchange (k(off) << k(et)). In short, these mutations indeed appear to have created the sought-for conversion from DD to simple docking (SD) energy landscapes.
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Affiliation(s)
- Peng Xiong
- Northwestern University, Department of Chemistry, 2145 Sheridan Road, Evanston, Illinois 60208, USA
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Volkov AN, Bashir Q, Worrall JAR, Ubbink M. Binding hot spot in the weak protein complex of physiological redox partners yeast cytochrome C and cytochrome C peroxidase. J Mol Biol 2008; 385:1003-13. [PMID: 19026661 DOI: 10.1016/j.jmb.2008.10.091] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 10/16/2008] [Accepted: 10/30/2008] [Indexed: 10/21/2022]
Abstract
Transient protein interactions mediate many vital cellular processes such as signal transduction or intermolecular electron transfer. However, due to difficulties associated with their structural characterization, little is known about the principles governing recognition and binding in weak transient protein complexes. In particular, it has not been well established whether binding hot spots, which are frequently found in strong static complexes, also govern transient protein interactions. To address this issue, we have investigated an electron transfer complex of physiological partners from yeast: yeast iso-1-cytochrome c (Cc) and yeast cytochrome c peroxidase (CcP). Using isothermal titration calorimetry and NMR spectroscopy, we show that Cc R13 is a hot-spot residue, as R13A mutation has a strong destabilizing effect on binding. Furthermore, we employ a double-mutant cycle to illustrate that Cc R13 interacts with CcP Y39. The present results, in combination with those of earlier mutational studies, have enabled us to outline the extent of the energetically important Cc-CcP binding region. Based on our analysis, we propose that binding energy hot spots, which are prevalent in static protein complexes, could also govern transient protein interactions.
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Affiliation(s)
- Alexander N Volkov
- Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands
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Current awareness on yeast. Yeast 2008. [DOI: 10.1002/yea.1557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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