European Biophysics Journal

, Volume 40, Issue 12, pp 1283–1299

Another look at the interaction between mitochondrial cytochrome c and flavocytochrome b2

Authors

    • Laboratoire de Chimie Physique, Faculté des SciencesUniversité Paris-Sud
Review

DOI: 10.1007/s00249-011-0697-0

Cite this article as:
Lederer, F. Eur Biophys J (2011) 40: 1283. doi:10.1007/s00249-011-0697-0

Abstract

Yeast flavocytochrome b2 tranfers reducing equivalents from lactate to oxygen via cytochrome c and cytochrome c oxidase. The enzyme catalytic cycle includes FMN reduction by lactate and reoxidation by intramolecular electron transfer to heme b2. Each subunit of the soluble tetrameric enzyme consists of an N terminal b5-like heme-binding domain and a C terminal flavodehydrogenase. In the crystal structure, FMN and heme are face to face, and appear to be in a suitable orientation and at a suitable distance for exchanging electrons. But in one subunit out of two, the heme domain is disordered and invisible. This raises a central question: is this mobility required for interaction with the physiological acceptor cytochrome c, which only receives electrons from the heme and not from the FMN? The present review summarizes the results of the variety of methods used over the years that shed light on the interactions between the flavin and heme domains and between the enzyme and cytochrome c. The conclusion is that one should consider the interaction between the flavin and heme domains as a transient one, and that the cytochrome c and the flavin domain docking areas on the heme b2 domain must overlap at least in part. The heme domain mobility is an essential component of the flavocytochrome b2 functioning. In this respect, the enzyme bears similarity to a variety of redox enzyme systems, in particular those in which a cytochrome b5-like domain is fused to proteins carrying other redox functions.

Keywords

Cytochrome b5Cytochrome cElectron transferFlavinFlavocytochrome b2Domain mobility

Abbreviations

Cyt. b5

Cytochrome b5

Cyt. c

Cytochrome c

CCP

Cytochrome c peroxidase

ET

Electron transfer

Fcb2

Flavocytochrome b2

FDH

Flavodehydrogenase

FeCya

Ferricyanide

Flred

Two-electron reduced flavin

Flsq

Flavin semiquinone

Flox

Oxidized flavin

IET

Intermolecular electron transfer

Hred

Reduced heme

Hox

Oxidized heme

WT

Wild type

Copyright information

© European Biophysical Societies' Association 2011