title: Direct electrochemistry of proteins. Investigations of yeast cytochrome c mutants and their complexes with cytochrome b5.
abstract: Direct electrochemistry of site-specific mutants of yeast iso-1-cytochrome c (cyt c) and their complexes with bovine cytochrome b5 (cyt b5) has been investigated at edge-plane pyrolytic graphite (EPG) and bis(4-pyridyl)-disulphide-modified gold electrodes. Structure/function relationships have been investigated with the particular aim of clarifying the factors controlling the interactions of proteins at electrode/electrolyte interfaces and the determinants for direct electrochemistry in ternary protein/protein/electrode adducts, e.g. cyt c/cyt b5/EPG. Investigations of the cyt c mutants alone revealed a variety of electrochemical responses: all the mutants show similar voltammetric reversibility at modified gold electrodes, whereas at EPG electrodes the reversibility follows the order: Asn52Ile-Cys102Thr greater than Cys102Thr greater than Asn52Ala-Cys102Thr. Mid-point potentials follow the order: Arg13Ile (+60 +/- 5 mV vs. standard calomel electrode) greater than Cys102Thr (+40 +/- 5 mV) greater than Lys27Gln (+30 +/- 5 mV) approximately Lys72Asp (+30 +/- 5 mV) greater than Asn52Ala-Cys102Thr (+15 +/- 5 mV) greater than Asn52Ile-Cys102Thr (-10 +/- 5 mV). The structural basis for these differences is briefly discussed. When these mutants are bound to cyt b5, the differences in electrochemical response are greatly enhanced in the ternary cyt c/cyt b5/EPG adducts. A minimal analysis of these differences supports a model of multiple overlapping binding and recognition domains on cyt c which may be finely tuned to allow ternary complex formation so that a single-site variation could modify or abolish direct electrochemistry in the ternary adduct.
authors.affiliation: Inorganic Chemistry Laboratory, Oxford, England.
authors.forename: A L
authors.initials: AL
authors.lastname: Burrows
authors.forename: L H
authors.initials: LH
authors.lastname: Guo
authors.forename: H A
authors.initials: HA
authors.lastname: Hill
authors.forename: G
authors.initials: G
authors.lastname: McLendon
authors.forename: F
authors.initials: F
authors.lastname: Sherman
mesh_terms: D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015786:Cytochromes b5 / Q000737:chemistry* / Q000378:metabolism; D045304:Cytochromes c; D004563:Electrochemistry; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: C014059:CYC1 protein, S cerevisiae; D003574:Cytochrome c Group; D029701:Saccharomyces cerevisiae Proteins; D045304:Cytochromes c; D015786:Cytochromes b5