Interaction and electron transfer between the high molecular weight cytochrome and cytochrome c3 from Desulfovibrio vulgaris Hildenborough: kinetic, microcalorimetric, EPR and electrochemical studies.

Abstract The complex formation between the tetraheme cytochrome c 3 and hexadecaheme high molecular weight cytochrome c (Hmc), the structure of which has recently been resolved, has been characterized by cross-linking experiments, EPR, electrochemistry and kinetic analysis, and some key parameters of the interaction were determined. The analysis of electron transfer between [Fe] hydrogenase, cytochrome c 3 and Hmc demonstrates a redox-shuttling role of cytochrome c 3 in the pathway from hydrogenase to Hmc, and shows an effect of redox state on the interaction between the two cytochromes. The role of polyheme cytochromes in electron transfer from periplasmic hydrogenase to membrane redox proteins is assessed. A model with cytochrome c 3 as an intermediate between hydrogenase and various polyheme cytochromes is proposed and its physiological consequences are discussed.