title: A T67A mutation in the proximal pocket of the high-spin heme of MauG stabilizes formation of a mixed-valent FeII/FeIII state and enhances charge resonance stabilization of the bis-FeIV state.
abstract: The diheme enzyme MauG catalyzes a six-electron oxidation required for posttranslational modification of a precursor of methylamine dehydrogenase (preMADH) to complete the biosynthesis of its protein-derived tryptophan tryptophylquinone (TTQ) cofactor. One heme is low-spin with ligands provided by His205 and Tyr294, and the other is high-spin with a ligand provided by His35. The side chain methyl groups of Thr67 and Leu70 are positioned at a distance of 3.4Å on either side of His35, maintaining a hydrophobic environment in the proximal pocket of the high-spin heme and restricting the movement of this ligand. Mutation of Thr67 to Ala in the proximal pocket of the high-spin heme prevented reduction of the low-spin heme by dithionite, yielding a mixed-valent state. The mutation also enhanced the stabilization of the charge-resonance-transition of the high-valent bis-FeIV state that is generated by addition of H2O2. The rates of electron transfer from TTQ biosynthetic intermediates to the high-valent form of T67A MauG were similar to that of wild-type MauG. These results are compared to those previously reported for mutation of residues in the distal pocket of the high-spin heme that also affected the redox properties and charge resonance transition stabilization of the high-valent state of the hemes. However, given the position of residue 67, the structure of the variant protein and the physical nature of the T67A mutation, the basis for the effects of the T67A mutation must be different from those of the mutations of the residues in the distal heme pocket.
authors.affiliation: Department of Bioengineering and Biotechnology, College of Engineering, Chonnam National University, Chonnam, South Korea.
authors.forename: Sooim
authors.initials: S
authors.lastname: Shin
authors.affiliation: Department of Chemistry, Tougaloo College, Tougaloo, MS 39174, USA.
authors.forename: Manliang
authors.initials: M
authors.lastname: Feng
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA.
authors.forename: Chao
authors.initials: C
authors.lastname: Li
authors.affiliation: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA.
authors.forename: Heather R
authors.initials: HR
authors.lastname: Williamson
authors.affiliation: Department of Optometry, College of Energy and Biotechnology, Seoul National University of Science and Technology, Seoul 139-743, South Korea.
authors.forename: Moonsung
authors.initials: M
authors.lastname: Choi
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA.
authors.forename: Carrie M
authors.initials: CM
authors.lastname: Wilmot
authors.affiliation: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA. Electronic address: victor.davidson@ucf.edu.
authors.forename: Victor L
authors.initials: VL
authors.lastname: Davidson
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D004579:Electron Transport; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism; D005296:Ferrous Compounds / Q000737:chemistry* / Q000378:metabolism; D006418:Heme / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006420:Hemeproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D045563:Indolequinones / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics*; D010084:Oxidation-Reduction; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000378:metabolism; D010231:Paracoccus denitrificans / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012242:Rhodobacter sphaeroides / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D013059:Spectrum Analysis, Raman; D014364:Tryptophan / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005290:Ferric Compounds; D005296:Ferrous Compounds; D006420:Hemeproteins; D045563:Indolequinones; C070569:tryptophan tryptophylquinone; D006418:Heme; D014364:Tryptophan; C021567:methylamine dehydrogenase; D000587:Oxidoreductases Acting on CH-NH Group Donors
keywords: Charge–resonance-transition; Cytochrome; Electron transfer; Ferryl; Heme; Metalloprotein