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Title Unimolecular and bimolecular oxidoreduction reactions involving diprotein complexes of cytochrome c and plastocyanin. Dependence of electron-transfer reactivity on charge and orientation of the docked metalloproteins
Creator/Author Peerey, L.M. ; Brothers, H.M. II ; Kostic, N.M. (Iowa State Univ., Ames (United States)) ; Hazzard, J.T. ; Tollin, G. (Univ. of Arizona, Tucson (United States))
Publication Date1991 Sep 24
OSTI IdentifierOSTI ID: 5822148
DOE Contract NumberW-7405-ENG-82
Other Number(s)ISSN0006-2960; CODEN: BICHA
Resource TypeJournal Article
Resource RelationBiochemistry ; Vol/Issue: 30:38; DOE Project
Subject550200 -- Biochemistry; METALLOPROTEINS-- BIOCHEMICAL REACTION KINETICS; CYTOCHROMES;DERIVATIZATION;ELECTRON TRANSFER;HEME;IMIDES;QUINONES;STEREOCHEMISTRY
Related SubjectAROMATICS;CARBOXYLIC ACIDS;CHEMICAL REACTIONS;HETEROCYCLIC ACIDS;HETEROCYCLIC COMPOUNDS;KINETICS;ORGANIC ACIDS;ORGANIC COMPOUNDS;ORGANIC NITROGEN COMPOUNDS;ORGANIC OXYGEN COMPOUNDS;PIGMENTS;PORPHYRINS;PROTEINS;REACTION KINETICS
Description/Abstract Cytochrome c and plastocyanin form an electrostatic complex, which can be reinforced by amide bonds in the presence of a carbodiimide.^Besides this cross-linking, carbodiimide also converts carboxylate side chains into neutral N-acylurea groups.^Four derivatives of the covalent diprotein complex, which differ in the degree of this charge neutralization, are separated by cation-exchange chromatography.^Electron-transfer reactions at different ionic strengths involving the electrostatic complex and the four derivatives of the covalent complex are studied by laser flash photolysis with flavin semiquiones as reducing agents.^The reactivity of the associated proteins toward external reductants cannot be predicted simply on the basis of this reactivity of the separate proteins.^Qualitative analysis of the dependence on ionic strength of the reactions between FMN semiquinone and the covalent derivatives indicates sites at which this reductant interacts with the cross-linked proteins.^The surprisingly small steric shielding of the protein redox sites in the covalent complex, as deduced from the reactions at high ionic strength, may indicate that the proteins have multiple reaction domains on their surfaces or that the complex is dynamical or both.^This reaction apparently requires a migration of cytochrome c from the acidic domain in plastocyanin, which is far from the copper redox site, to the hydrophobic domain, which is near this site.
Country of PublicationUnited States
LanguageEnglish
FormatPages: 9297-9304
System Entry Date2001 May 13

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