Factors influencing intermolecular and intramolecular electron transfer in the cytochrome c: Cytochrome c peroxidase complex.

Persistent Link:
http://hdl.handle.net/10150/184957
Title:
Factors influencing intermolecular and intramolecular electron transfer in the cytochrome c: Cytochrome c peroxidase complex.
Author:
Hazzard, James Taylor.
Issue Date:
1989
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The kinetics of reduction by free flavin semiquinones of the individual components of 1:1 complexes of yeast cytochrome c peroxidase and the cytochrome c from horse, tuna, and yeast, including several site-specific mutants of either the cytochrome c or cytochrome c peroxidase, have been studied. The orientations of the various cytochromes c within electrostatically-stabilized complexes with the peroxidase are not equivalent. This is shown by differential decreases in the rate constants for cytochrome reduction by neutral flavin semiquinones upon complexation which are in the order: tuna ≫ horse > yeast iso-2 > yeast iso-1. We have also directly measured the physiologically-significant intracomplex one-electron transfer rate constants from the ferrous cytochromes c to the peroxide-oxidized species of the peroxidase at several ionic strengths. The rate constants at low ionic strength are highly species dependent, again consistent with the contention that the orientations of the various cytochromes within the complex with CcP are not the same. Increasing the ionic strength in all cases resulted in an increase in the rate constant for the first-order process which controls electron transfer from cytochrome c to the peroxidase Compound I species of the peroxidase. When the two proteins are immobilized by covalent cross-linking, no such rate enhancement is observed, suggesting that the ionic strength effect is manifested by an increase in the number of geometric orientations between the two proteins which results in more rapid electron transfer. Similar rate enhancing effects are observed when positively charged residues on the surface of cytochrome c are converted to electrostatically neutral amino acids by site-specific mutagenesis. The effect of site-specific mutagenesis of two residues of cytochrome c peroxidase have also been studied. His-181, when converted to a glycine has little effect on the electron transfer rate constant, whereas when Trp-191 is converted to a phenylalanine no intracomplex electron transfer could be observed, indicating an obligatory role of this residue in the electron transfer process.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Oxidation-reduction reaction -- Mathematical models; Cytochrome c; Chemical kinetics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Biochemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Tollin, Gordon

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleFactors influencing intermolecular and intramolecular electron transfer in the cytochrome c: Cytochrome c peroxidase complex.en_US
dc.creatorHazzard, James Taylor.en_US
dc.contributor.authorHazzard, James Taylor.en_US
dc.date.issued1989en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe kinetics of reduction by free flavin semiquinones of the individual components of 1:1 complexes of yeast cytochrome c peroxidase and the cytochrome c from horse, tuna, and yeast, including several site-specific mutants of either the cytochrome c or cytochrome c peroxidase, have been studied. The orientations of the various cytochromes c within electrostatically-stabilized complexes with the peroxidase are not equivalent. This is shown by differential decreases in the rate constants for cytochrome reduction by neutral flavin semiquinones upon complexation which are in the order: tuna ≫ horse > yeast iso-2 > yeast iso-1. We have also directly measured the physiologically-significant intracomplex one-electron transfer rate constants from the ferrous cytochromes c to the peroxide-oxidized species of the peroxidase at several ionic strengths. The rate constants at low ionic strength are highly species dependent, again consistent with the contention that the orientations of the various cytochromes within the complex with CcP are not the same. Increasing the ionic strength in all cases resulted in an increase in the rate constant for the first-order process which controls electron transfer from cytochrome c to the peroxidase Compound I species of the peroxidase. When the two proteins are immobilized by covalent cross-linking, no such rate enhancement is observed, suggesting that the ionic strength effect is manifested by an increase in the number of geometric orientations between the two proteins which results in more rapid electron transfer. Similar rate enhancing effects are observed when positively charged residues on the surface of cytochrome c are converted to electrostatically neutral amino acids by site-specific mutagenesis. The effect of site-specific mutagenesis of two residues of cytochrome c peroxidase have also been studied. His-181, when converted to a glycine has little effect on the electron transfer rate constant, whereas when Trp-191 is converted to a phenylalanine no intracomplex electron transfer could be observed, indicating an obligatory role of this residue in the electron transfer process.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectOxidation-reduction reaction -- Mathematical modelsen_US
dc.subjectCytochrome cen_US
dc.subjectChemical kinetics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineBiochemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorTollin, Gordonen_US
dc.contributor.committeememberCusanovich, Micheal A.en_US
dc.contributor.committeememberDeatherage, James F.en_US
dc.contributor.committeememberMeyer, Terrence E.en_US
dc.contributor.committeememberForster, Leslie S.en_US
dc.identifier.proquest9016331en_US
dc.identifier.oclc24003248en_US
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