title: Crystal structures of CO and NO adducts of MauG in complex with pre-methylamine dehydrogenase: implications for the mechanism of dioxygen activation.
abstract: MauG is a diheme enzyme responsible for the post-translational formation of the catalytic tryptophan tryptophylquinone (TTQ) cofactor in methylamine dehydrogenase (MADH). MauG can utilize hydrogen peroxide, or molecular oxygen and reducing equivalents, to complete this reaction via a catalytic bis-Fe(IV) intermediate. Crystal structures of diferrous, Fe(II)-CO, and Fe(II)-NO forms of MauG in complex with its preMADH substrate have been determined and compared to one another as well as to the structure of the resting diferric MauG-preMADH complex. CO and NO each bind exclusively to the 5-coordinate high-spin heme with no change in ligation of the 6-coordinate low-spin heme. These structures reveal likely roles for amino acid residues in the distal pocket of the high-spin heme in oxygen binding and activation. Glu113 is implicated in the protonation of heme-bound diatomic oxygen intermediates in promoting cleavage of the O-O bond. Pro107 is shown to change conformation on the binding of each ligand and may play a steric role in oxygen activation by positioning the distal oxygen near Glu113. Gln103 is in a position to provide a hydrogen bond to the Fe(IV)═O moiety that may account for the unusual stability of this species in MauG.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 321 Church Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Erik T
authors.initials: ET
authors.lastname: Yukl
authors.forename: Brandon R
authors.initials: BR
authors.lastname: Goblirsch
authors.forename: Victor L
authors.initials: VL
authors.lastname: Davidson
authors.forename: Carrie M
authors.initials: CM
authors.lastname: Wilmot
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D055162:Biocatalysis; D002248:Carbon Monoxide / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003578:Cytochrome-c Peroxidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005296:Ferrous Compounds / Q000737:chemistry; D018698:Glutamic Acid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006418:Heme / Q000737:chemistry / Q000378:metabolism; D006420:Hemeproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D045563:Indolequinones / Q000737:chemistry / Q000378:metabolism; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D010088:Oxidoreductases / Q000378:metabolism; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010231:Paracoccus denitrificans / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry; D013379:Substrate Specificity; D014364:Tryptophan / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005296:Ferrous Compounds; D006420:Hemeproteins; D045563:Indolequinones; C070569:tryptophan tryptophylquinone; D009569:Nitric Oxide; D018698:Glutamic Acid; D006418:Heme; D002248:Carbon Monoxide; D014364:Tryptophan; D010088:Oxidoreductases; D003578:Cytochrome-c Peroxidase; C021567:methylamine dehydrogenase; D000587:Oxidoreductases Acting on CH-NH Group Donors; C090099:diheme cytochrome c; D010100:Oxygen