title: Enzymatic and electron transfer activities in crystalline protein complexes.
abstract: Enzymatic and electron transfer activities have been studied by polarized absorption spectroscopy in single crystals of both binary and ternary complexes of methylamine dehydrogenase (MADH) with its redox partners. Within the crystals, MADH oxidizes methylamine, and the electrons are passed from the reduced tryptophan tryptophylquinone (TTQ) cofactor to the copper of amicyanin and to the heme of cytochrome c551i via amicyanin. The equilibrium distribution of electrons among the cofactors, and the rate of heme reduction after reaction with substrate, are both dependent on pH. The presence of copper in the ternary complex is not absolutely required for electron transfer from TTQ to heme, but its presence greatly enhances the rate of electron flow to the heme.
authors.affiliation: Istituto di Scienze Biochimiche, Universita di Parma, Parma, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Merli
authors.forename: D E
authors.initials: DE
authors.lastname: Brodersen
authors.forename: B
authors.initials: B
authors.lastname: Morini
authors.forename: Z
authors.initials: Z
authors.lastname: Chen
authors.forename: R C
authors.initials: RC
authors.lastname: Durley
authors.forename: F S
authors.initials: FS
authors.lastname: Mathews
authors.forename: V L
authors.initials: VL
authors.lastname: Davidson
authors.forename: G L
authors.initials: GL
authors.lastname: Rossi
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D003300:Copper; D003460:Crystallization; D003574:Cytochrome c Group / Q000737:chemistry* / Q000378:metabolism; D004579:Electron Transport; D006418:Heme; D045563:Indolequinones; D046911:Macromolecular Substances; D008961:Models, Structural; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D011809:Quinones / Q000378:metabolism; D013053:Spectrophotometry / Q000379:methods; D014364:Tryptophan / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; D045563:Indolequinones; D046911:Macromolecular Substances; D011809:Quinones; C017079:mauC protein, Methylobacterium extorquens; C070569:tryptophan tryptophylquinone; D006418:Heme; D003300:Copper; D014364:Tryptophan; C017167:cytochrome C(551); C021567:methylamine dehydrogenase; D000587:Oxidoreductases Acting on CH-NH Group Donors