title: Metal-free and metal-substituted cytochromes c. Use in characterization of the cytochrome c binding site.
abstract: The luminescent properties of metal-free, tin(IV) and zinc(II) cytochromes c have been used to characterize the interaction of cytochrome c with mitochondria and cytochrome oxidase. Diminution in the fluorescence yields of tin and zinc cytochrome c occur when these derivates bind to cytochrome oxidase or mitochondria. Based upon spectral overlap and quantum yield, the distance between the porphyrin rings of cytochrome a and cytochrome c is estimated according to Forster theory to be in the neighborhood of 3.5 nm. Measurements of the polarized emission of metal-free 'porphyrin' cytochrome c when bound to oriented layers of cytochrome c oxidase indicate that the porphyrin is bound obliquely to the plane of the oxidase layers with an angle of about 70 degrees C from heme plane to membrane plane. It is proposed that these data have significance for elucidation of electron transfer mechanisms.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003574:Cytochrome c Group; D003576:Electron Transport Complex IV; D007700:Kinetics; D008345:Manganese; D008930:Mitochondria, Liver; D009206:Myocardium / Q000201:enzymology; D011166:Porphyrins; D011485:Protein Binding; D051381:Rats; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D013696:Temperature; D014001:Tin; D015032:Zinc
chemical_list: D003574:Cytochrome c Group; D011166:Porphyrins; D008345:Manganese; D014001:Tin; D003576:Electron Transport Complex IV; D015032:Zinc