Tetraheme cytochromes c3 constitute the best-studied group among the multiheme cytochromes belonging to the class III of Ambler's classification. Since 1954, when cytochrome c3 was isolated from Desulfovibrio vulgaris for the first time by Postgate, these proteins have been widely characterized, especially those from the Desulfovibrio (D.) genus. All these cytochromes have their heme group attached to the polypeptide chain by cysteine residues and show bis-histidinyl coordination of the heme iron and a highly conserved heme-binding motif (CXXCH or CXXXXCH). Cytochromes c3 show a wide variety of redox potentials, ranging from 0 to -400mV, are usually periplasmatic proteins, and are believed to play key roles in the electron transfer chains. Recently, the cytochrome c3 group was divided into two main types on the basis of structural, functional, and genetic differences: type I cytochrome c3 (TpI- c3) and type II cytochrome c3 (TpII-c3). This paper reviews their structural, spectroscopic, and functional properties, based on the wealth of information currently available. These include physicochemical properties, redox mechanisms, coupling between electron and proton transfer, and data concerning the interaction with their redox partners obtained by experimental and molecular modeling methods.
|Title of host publication||Encyclopedia of Inorganic and Bioinorganic Chemistry|
|Place of Publication||Chichester|
|Publisher||John Wiley & Sons|
|Publication status||Published - 1 Jan 2011|