Kinetic studies of electron transfer between hydrogenase and cytochrome c3 from Desulfovibrio gigas. Electrochemical properties of cytochrome c3

Abstract

The second-order rate constant of the electron transfer between cytochrome c 3 ( M r 13 000) and hydrogenase from Desulfovibrio gigas has been determined by spectrophotometry and cyclic voltammetry. Both of these methods gave the same value of 6.5 · 10 7 M −1 · s −1. Comparative measurements for other protein-protein interactions show that the foregoing value is relatively high and comparable with that obtained for two other physiological partners, cytochrome c 3 and hydrogenase from Desulfovibrio desulfuricans Norway. In addition, the redox potentials of the four hemes of D. gigas cytochrome c 3 have been measured by polarography. These values were estimated to be −195, −295, −315 and −330 mV.