Electrostatic effect on electron transfer between cytochrome b(5) and cytochrome c

The binding and electron transfer between wild type, E44A, E56A, E44/56A, E 44/48/56A/D60A and F35Y variants of cytochrome b(5) and cytochrome c were s tudied. When mixed with cytochrome c, the cytochrome b(5) E44/48/56A/D60A d id not show the typical UV-vis difference spectrum of absorption, indicatin g that the alteration of the surface electrostatic potential obviously infl uenced the spectrum. The electron transfer rates of wild type cytochrome b( 5), its variants and cytochrome c at different temperature and ionic streng th exhibited an order of F35Y > wild type > E56A > E44A > E44/48/56A/D60A. The enthalpy and entropy of the reaction did not change obviously, suggesti ng that the mutation did not significantly disturb the electron transfer co nformation. The investigation of electron transfer rate constants at differ ent ionic strength demonstrated that electrostatic interaction obviously af fected the electron transfer process. The significant difference of Cyt b(5 ) F35Y and E44/48/56A/D60A from the wild type protein further confirmed the great importance of the electrostatic interaction in the protein electron transfer.