Methylamine dehydrogenase electron cytochrome

Davidson, V. L., and Jones, L. H., 1996, Electron transfer from copper to heme within the methylamine dehydrogenase-amicyanin-cytochrome C-55H complex. Biochemistry 35 8120n8125. 

Chen, L., Durley, R., Mathews, F. S., and Davidson, V. L., 1994, Structure of an electron transfer complex Methylamine dehydrogenase, amicyanin and cytochrome c-551i. Science 264 86990. 

Amicyanin is found in methylotrophic bacteria that can use methylated amines as an energy source. The inactivation of the amicyanin gene in Paracoccus denitrificans results in complete loss of its ability to grow on methylamine, a direct indication that amicyanin is a key component of the methylamine driven electron-transfer chain. Amicyanin accepts an electron from methylamine dehydrogenase and transfers it to a c-type cytochrome (see Section 5.4.5). Currently, more than a dozen amicyanin and pseudoazurin sequences are available. 

Two amicyanins from the methylotropic bacteria Pseudomonas AMI and T. versutus have been a recent focus of attention (42, 43). Their function is to mediate electron transfer between bacterial cytochrome c and methylamine dehydrogenase in a relatively short electron transport chain. 

Amicyanins function as electron carriers in the respiratory chains of some me-thylotrophic bacteria, e.g., Thiobacillus versutus [92]. They transfer single electrons from methylamine dehydrogenase to a cytochrome c [78] which then transfers the electron to cytochrome c oxidase. Amicyanin from Pseudomonas denitrificans has a molecular mass of 11.6 kD and contains 106 amino acid residues. Amicyanin contains one /J-sheet more than the eight of plastocyanin and pseudoazurin, the result of several additional amino acids at its N-terminus [78] (Fig. 15). Like pseudoazurin, amicyanin is found exclusively in bacteria. 

Aromatic residues have been found in proteins at positions that probably enhance the electronic coupling in systems that have been selected by evolution for efficient ET. Examples are the tryptophan mediated reduction of quinone in the photosynthetic reaction center (31), the methylamine dehydrogenase (MADH) amicyanin system, where a Trp residue is placed at the interface between the two proteins (32), as well as the [cytochrome c peroxidase-cytochrome c] complex, where a Trp seems to have a similar function (33). 

Pathways can yield reliable predictions of the electronic couplings, where the CT process in proteins are mediated by the interactions of a single or multiple configurations that the protein can adopt [50]. Pathways has been successfully applied to a number of CT processes in protein environment. For instance, the electron transfer between the proteins cytochrome c2 (cytc2) and the photosynthetic reaction center (RC) [152] in order to determine the protein structural dependence of this CT reaction, also, to look at the impact of structural and conformational variations on the electronic coupling between the proteins methylamine dehydrogenase and amicyanin from Paracoccus denitrificans [153]. 

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