Accelerated Evolution of Cytochrome <i>c</i> in Higher Primates, and Regulation of the Reaction between Cytochrome <i>c</i> and Cytochrome Oxidase by Phosphorylation
Sue Ellen Brand,
Martha Scharlau,
Lois Geren,
Marissa Hendrix,
Clayre Parson,
Tyler Elmendorf,
Earl Neel,
Kaila Pianalto,
Jennifer Silva-Nash,
Bill Durham,
Francis Millett
Affiliations
Sue Ellen Brand
North Murray High School, Chatsworth, GA 30705, USA
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
Jennifer Silva-Nash
Independent Researcher, 5 Kingdom Court, Maumelle, AR 72113, 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
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.
