title: 31P-NMR of free and protein-bound molybdopterin guanine dinucleotide.
abstract: Molybdopterin guanine dinucleotide was studied by 31P-NMR in the free, iodoacetamide derivatized form [di(carboxamidomethyl)molybdopterin] and in the native state in the dimethyl sulfoxide reductase from Rhodobacter sphaeroides. The spectra confirm the presence of a pyrophosphate moiety in the cofactor molecule. Comparison of the spectrum of the free pterin with that of the protein-bound cofactor reveals a substantial upfield shift of the 31P resonances in the enzyme-bound form with respect to the free form. This shift is attributed to differences in the bond and torsional angles of the phosphates. The spectrum of the protein suggests significant coupling between the two phosphorus nuclei with coupling constants of approximately 200 Hz. Comparison of the 31P-NMR spectra of molybdopterin guanine dinucleotide and flavin adenine dinucleotide suggests that the two cofactors have similar conformations in both their free and protein-bound forms.
authors.affiliation: Department of Biochemistry, Duke University Medical Center, Durham, NC 27710.
authors.forename: N R
authors.initials: NR
authors.lastname: Bastian
authors.forename: J L
authors.initials: JL
authors.lastname: Johnson
authors.forename: K V
authors.initials: KV
authors.lastname: Rajagopalan
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006150:Guanine Nucleotides / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D010761:Phosphorus Radioisotopes; D011485:Protein Binding; D011622:Pterins / Q000032:analysis*; D012242:Rhodobacter sphaeroides
chemical_list: D006150:Guanine Nucleotides; D010761:Phosphorus Radioisotopes; D011622:Pterins; C063761:molybdopterin guanine dinucleotide