The Electron Transfer Function of Cytochrome c

Amino acid sequence, haem-iron co-ordination geometry and functional properties of mitochondrial and bacterial c-type cytochromes

“…Thus, cytochromes are present not only in the aerobic mitochondrial and bacterial respiratory chain, but are also found in much more diversified procariotic systems, including all varieties of facultative anaerobes (nitrate and nitrite reducers), obligate anaerobes (sulphate reducers and phototrophic sulphur bacteria), facultative photoheterotrophes (phototrophic non-sulphur purple bacteria), and the photoautotrophic cyanobacteria (blue-green algae). Among the different types of cytochromes occurring in the cell, the soluble c-type cytochromes ('class I', Meyer & Kamen, 1982) are the most abundant and best characterized group of proteins (Bartsch, 1978;Meyer & Kamen, 1982;Dickerson & Timkovitch, 1975;Lemberg & Barrett, 1973;Salemme, 1977;Ferguson-Miller, Brautigan & Margoliash, 1979). The amino acid sequences of more than 80 mitochrondrial and close to 40 bacterial cytochromes c are known (Meyer & Kamen, 1982;Dickerson & Timkovitch, 1975;Schwartz & Dayhoff, 1976;Dayhoff & Barker, 1978).…”

“…A search for the biochemical rational behind the persistent occurrence of histidine and methionine as axial ligands of the haem-iron has been our motivation for systematic studies of correlations between the active site conformation and the primary structure, the electronic structure of haem c and functional properties, such as the redox potential or the reactivity with cytochrome oxidases and reductases from different species. The omnipresence of soluble c-type cytochromes in nature has already stimulated many comparative structural (Dickerson & Timkovitch, 1975;Timkovitch, 1979;Moore et al 1982), evolutionary (Meyer & Kamen, 1982;Dickerson, 19800,6,c) and functional studies (Ferguson-Miller et al 1979;Errede & Kamen, 1978;Yamanaka & Okunuki, 1968;Sutin, 1977). Thereby the characterization of the protein surface responsible for the interaction with physiological redox-partners has been the target of numerous recent biochemical investigations (Ferguson-Miller et al 1979;Rieder & Bosshard, 1980;Waldmeyer et al 1982;Kraut, 1981).…”

“…The omnipresence of soluble c-type cytochromes in nature has already stimulated many comparative structural (Dickerson & Timkovitch, 1975;Timkovitch, 1979;Moore et al 1982), evolutionary (Meyer & Kamen, 1982;Dickerson, 19800,6,c) and functional studies (Ferguson-Miller et al 1979;Errede & Kamen, 1978;Yamanaka & Okunuki, 1968;Sutin, 1977). Thereby the characterization of the protein surface responsible for the interaction with physiological redox-partners has been the target of numerous recent biochemical investigations (Ferguson-Miller et al 1979;Rieder & Bosshard, 1980;Waldmeyer et al 1982;Kraut, 1981). In contrast, there have been few comparative studies of the structure of the active centre of cytochromes c. This centre lies in the interior of the protein and consists of the haem group and two axial T A B L E I.…”

“…The apparent free energy of electron transfer would be lowered as a result of this conformation change. Experimental support for the potential of c-type cytochromes to adopt such intermediate structures comes from single crystal X-ray studies (Takano & Dickerson, 19810,6;Matsuura et al 1982), chemical modification (Ferguson-Miller et al 1979;Osheroff et al 1979Osheroff et al , 1980Koppenol & Margoliash, 1982) and NMR studies (Moore et al 1982;Senn et al 1983 a, 19846;Keller & Wiithrich, 1981). These studies also show that the biologically interacting surface of the globular molecule lies close to the axial methionine and is conformationally rather flexible.…”

“…The surface topology and charge distribution in cytochromes c have been recognized as important structural determinants for the function of the molecule within its specific enzyme system (Errede & Kamen, (Horio, 1958;Yamanaka & Okunuki, 1968;Errede & Kamen, 1978;Meyer & Kamen, 1982) Also named as cytochrome cd-nitrit reductase (Meyer & Kamen, 1982Ferguson-Miller et al 1979). Differences in the enzymatic activity of various chemically modified horse cytochromes could be quantitatively related to changes in the orientation of the electric dipole moments (Ferguson-Miller et al 1979;Koppenol & Margoliash, 1982).…”