[Effect of tyrosine-74-modified cytochrome C on electron transfer in Keilin-Hartree submitochondrial particles]

The tyrosine-74 modified cytochrome c is obtained by the interaction of cytochrome c with N-(2, 2, 5, 5-tetramethyl-3-carboxy-piroline-oxyl) Imidazol. The absorbtion spectrum of the modified derivative at the visible region does not differ substantially from the native protein. The band of absorbtion at 695 nm, which shows that the performed modification is soft and the conformation of the modified cytochrome c is close to that of the native protein. Redox potential of the modified cytochrome c, determined by spectrophotometric titration, does not differ from that of the native protein. Submitochondrial particles, deficient of cytochrome c, are reconstructed with modified protein. In both substrates of biologic oxidation succinate and ascorbate the electron transport is restored by the modified protein in considerably higher concentrations than those of the native cytochrome c. Inspite of small conformation differences and unchanged redox potential of the modified cytochrome c substantial differences are observed in its electron-carrying properties as well as its interaction with the membrane cytochrome c reductase and oxydase.