Another look at the interaction between mitochondr

Authors: Florence Lederer

Publish Date: 2011/04/19

Volume: 40, Issue: 12, Pages: 1283-1299

PDF Link

Abstract

Yeast flavocytochrome b 2 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 b 2 Each subunit of the soluble tetrameric enzyme consists of an N terminal b 5like hemebinding 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 b 2 domain must overlap at least in part The heme domain mobility is an essential component of the flavocytochrome b 2 functioning In this respect the enzyme bears similarity to a variety of redox enzyme systems in particular those in which a cytochrome b 5like domain is fused to proteins carrying other redox functions

Keywords: