title: Estimation of the distance between the divalent cation binding site of des-1-41-light chain-activated bovine plasma protein C and a nitroxide spin label attached to the active-site serine residue.
abstract: The paramagnetic effect of Mn2+ on the electron paramagnetic resonance spectrum of a nitroxide spin label covalently attached to the active-site serine residue of des-1-41-light chain bovine plasma-activated protein C, and situated at a distance of approximately 1.2 nm from this amino acid, has been utilized to estimate the distance on the enzyme surface between the single Mn2+ site and the free electron of the spin label. This distance has been found to be approx. 1.12 nm. A significant paramagnetic effect of Mn2+ on the spectrum of this same nitroxide spin label bound to activated protein C (APC) has been found. However, in this case distance calculations are complicated by the existence of a multiplicity of Mn2+ sites on APC. If it is assumed that a single Mn2+ site is responsible for the paramagnetic effect on the spectrum of the spin label, the interelectron distance on APC would be approx. 0.90 nm.
authors.affiliation: Department of Chemistry, University of Notre Dame, IN 46556.
authors.forename: K A
authors.initials: KA
authors.lastname: Hill
authors.forename: S A
authors.initials: SA
authors.lastname: Steiner
authors.forename: F J
authors.initials: FJ
authors.lastname: Castellino
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy; D008345:Manganese / Q000378:metabolism*; D009589:Nitrogen Oxides / Q000032:analysis*; D010446:Peptide Fragments / Q000378:metabolism*; D011486:Protein C / Q000378:metabolism*; D012694:Serine / Q000032:analysis; D013113:Spin Labels
chemical_list: D003497:Cyclic N-Oxides; D009589:Nitrogen Oxides; D010446:Peptide Fragments; D011486:Protein C; D013113:Spin Labels; C050706:protein C, des-1-41 light chain activated-; D008345:Manganese; D012694:Serine; C056445:4-(2,2,5,5-tetramethylpyrrolidine-1-oxyl)-4-fluorosulfonylbenzamide