title: Why do c-type cytochromes exist? Reprise.
abstract: An earlier paper (Wood, P.M. (1983) FEBS Lett. 164, 223-226) proposed that the covalent links that characterize c-type haem originated in order to prevent the haem being lost into the external medium. This is discussed in relation to Gram-negative and Gram-positive bacteria, cyanobacterial thylakoids and eukaryotes. The practical application is for unravelling complex electron transfer chains: c-type cytochromes may be assumed to be absent from the cytoplasm. Sulphate reducing bacteria provide the only confirmed exception to this rule. Examples of non-covalent haem at risk of being lost are considered. Analogies are drawn with flavin and pyrroloquinoline quinone as prosthetic groups.
authors.affiliation: Department of Biochemistry, University of Bristol, U.K.
authors.forename: P M
authors.initials: PM
authors.lastname: Wood
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001665:Binding Sites; D000458:Cyanobacteria / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004579:Electron Transport; D005415:Flavins / Q000378:metabolism; D006418:Heme / Q000378:metabolism; D010084:Oxidation-Reduction; D011809:Quinones / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism
chemical_list: D003574:Cytochrome c Group; D005415:Flavins; D011809:Quinones; D013431:Sulfates; D006418:Heme