title: Maturation of a eukaryotic cytochrome c in the cytoplasm of Escherichia coli without the assistance by a dedicated biogenesis apparatus.
abstract: Maturation of c-type cytochromes involves the covalent and stereospecific enzymatic attachment of a heme b via thioether linkages to two conserved cysteines within apocytochromes. Horse cytochrome c is readily matured into its native holoform in the cytoplasm of E. coli when co-expressed with yeast cytochrome c heme lyase. Here we report the low yield formation of holocytochrome with covalently attached heme also in the absence of heme lyase. This is the first demonstration of in vivo maturation of a eukaryotic cytochrome c in a prokaryotic cytoplasm without the assistance by a dedicated enzymatic maturation system. The assembled cytochrome c can be oxidized by cytochrome c oxidase, indicating the formation of a functional protein. The absorption spectrum is typical of a low spin, six coordinated c-type heme. Nevertheless, minor spectral differences relative to the native cytochrome c, deviation of the midpoint reduction potential and slightly altered kinetic parameters of the interaction with cytochrome c oxidase emphasize the importance of cytochrome c heme lyase in folding cytochrome c into its native conformation.
authors.affiliation: Institute of Biophysics, Biological Research Center of the Hungarian Academy of Sciences, P.O.Box 521, Szeged, 6701, Hungary.
authors.forename: Katalin
authors.initials: K
authors.lastname: Tenger
authors.forename: Petro
authors.initials: P
authors.lastname: Khoroshyy
authors.forename: Gábor
authors.initials: G
authors.lastname: Rákhely
authors.forename: László
authors.initials: L
authors.lastname: Zimányi
mesh_terms: D000818:Animals; D045304:Cytochromes c / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D006736:Horses / Q000235:genetics*
chemical_list: D006418:Heme; D045304:Cytochromes c; D003576:Electron Transport Complex IV