Amicyanin is a type I copper protein that plays an integral role in electron transfer. In
bacteriasuch as " Paracoccus denitrificans" amicyanin is part of a three member redox complexalong with methylamine dehydrogenase(MADH) and cytochromec-551i.
In the electron transfer mechanism from MADH to
hemeamicyanin acts as an electron accepting intermediate. In this reaction MADH catalyzes the oxidative deamination of methylamineto formaldehydeplus ammonia. The tryptophan tryptophylquinone(TTQ) group of MADH then donates electrons to the copper center of amicyanin, which in turn gives the electrons to the heme of the cytochrome c. In "P. denitrificans" amicyanin is absolutely required for electron transfer from MADH to c-type cytochromes. It has been shown inactivation of amicyanin by gene replacement in vivo results in complete loss of ability to grow on methylamine.
As a type I copper protein amicyanin contains one copper atom coordinated by two
histidineresidues and a cysteineresidue in a trigonal planerstructure along with an axial methionineresidue ligand. Alterations from this particular coordination of the copper center are found to negatively alter the redox potential of amicyanin. In "P. denitrificans" amicyanin exists in a three part complex along with MADH and cytochrome c-551i. This is the only redox complex comprised of three weakly associated proteins naturally observed.
1. Victor L. Davidson and Limei Hsu Jones, "Biochemistry" 1996, 35, 8120-8125.
2. Arnout P. Kalverda, Jesus Salgado, Christopher Dennison, and Gerard W. Canters, "Biochemistry" 1996, 35, 3085-3092.
3. Victor L. Davidson and Dapeng Sun, "J. Am. Chem. Soc." 2003, 125, 3224-3225.
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