Methylamine dehydrogenase protein complex

Davidson, V. L., Graichen, M. E., and Jones, L. H., 1993, Binding constants for a physiologic electron-transfer protein complex between methylamine dehydrogenase and amicyanin. Effects of ionic strength and bound copper on binding, Biochim. Biophys. Acta 1144 3 9n 45. 

Three-dimensional structures. The TPQ-con-taining amine oxidase from E. coU is a dimer of 727-residue subunits with one molecule of TPQ at position 402 in each subunit. 7458 Methylamine dehydrogenase is also a large dimeric protein of two large 46.7-kDa subunits and two small 15.5-kDa subunits. Each large subunit contains a TTQ cofactor Reduced TTQ is reoxidized by the 12.5-kDa blue copper protein amicyanin. Crystal structures have been determined for complexes of methylamine dehydrogenase with amicyanin and of these two proteins with a third protein, a small bacterial cytochrome... 

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). 

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