title: Bile pigment--protein interactions. Coupled oxidation of cytochrome c.
abstract: A new methodology is described for the chemical modification of the heme prosthetic group of horse heart cytochrome c. The selective modification of the heme moiety of cytochrome c is facilitated by utilizing coupling oxidation conditions. Comparison of the absorption spectra of this chemically modified cytochrome c species in two different solvents (aqueous pyridine and carbon monoxide saturated 6 M guanidinium chloride) with those of two model compounds [bis(pyridine)(2,3,7,8,12,13,17,18-octaethyl-5-oxaporphyrinato)iron(II) tetrafluoroborate salt and (pyridine)carbonyl-(2,3,7,8,12,13,17,18-octaethyl-5-oxaporphyrinato)iron(II) tetrafluoroborate salt] shows that coupled oxidation of cytochrome c affords a new protein with a covalently bound iron(II) oxaporphyrin prosthetic group. Amino acid analysis of this protein-bound iron(II) oxaporphyrin species reveals that only limited modification of the primary structure of the apoprotein occurs during coupled oxidation of cytochrome c. This protein-bound iron(II) oxaporphyrin species is also interconvertible to a protein-bound bilatriene species under hydrolytic conditions. The synthetic utility of the coupled oxidation of cytochrome c for the preparation of chromoproteins which possess covalently bound iron(II) oxaporphyrin and bilatriene prosthetic groups is considered.
mesh_terms: D000596:Amino Acids; D001654:Bile Pigments; D002248:Carbon Monoxide; D055598:Chemical Phenomena; D002621:Chemistry; D003574:Cytochrome c Group; D019791:Guanidine; D006146:Guanidines; D010084:Oxidation-Reduction; D011166:Porphyrins; D011725:Pyridines; D012997:Solvents; D013053:Spectrophotometry
chemical_list: D000596:Amino Acids; D001654:Bile Pigments; D003574:Cytochrome c Group; D006146:Guanidines; D011166:Porphyrins; D011725:Pyridines; D012997:Solvents; D002248:Carbon Monoxide; D019791:Guanidine