Electron-transport assemblies protein complexes

TABLE 13.1 The composition of the protein complexes of the electron-transport assemblies of bovine heart mitochondria... 

Although the whole-cell membrane is non-conductive, there are several redox proteins anchored on/in the membrane that confer nano-scale conductivity to the membrane and directly enable electron transfer across the cell membrane. These proteins usually assemble together in the periplasm and/or on/across the outer-surface membrane and act as an electron transfer chain to relay the electron across the membrane. For example, the membrane-bound electron transfer chain of Shewanella oneidensis is a trans icosa-heme complex, MtrCAB, that can move electrons across the membrane. The MtrC is a decaheme cytochrome located on the outside of the outer cell membrane that mediates the electron transfer to the extracellular substrate e.g, solid electrode). MtrAB is the transmembrane electron transfer module that is responsible for electron transport from the periplasm to MtrC. More interestingly, recent findings indicates that this electron conduit is capable of reverse electron transfer, ie., electron up-take from extracellular electrodes. ... 

Embedded within the inner membrane are the protein electron carriers (primarily) cytochromes, which constitute the respiratory chain. They are assembled in the form of five multiprotein complexes, named I, II, III, IV, and V. Smaller carriers, such as coenzyme Q and cytochrome c, also participate in carrying electrons. Figure 15.2b shows metabolic reactions occuring inside the mitochondrial matrix and movement of electrons through the complexes in the inner mitochondrial membrane. Note that electrons are ultimately donated with protons to oxygen to form water and that Complex V does not function in transport of electrons. 

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