title: The positions of radical intermediates in the active sites of adenosylcobalamin-dependent enzymes.
abstract: The radical intermediates generated during the catalytic cycles of adenosylcobalamin-dependent enzymes occur in pairs. The positions of radicals residing on the cofactor, substrate or protein, relative to the position of the low-spin Co(2+) from the cob(II)alamin intermediate, can be extracted from electron paramagnetic resonance (EPR) spectra of the spin-coupled pairs. Examples of radical-Co(2+) pairs that span a range of interspin distances from 3 to 13A have been presented. Interspin distances greater than 5A require motion of one or more of the participating species. EPR spectroscopy provides a convenient means to determine the structures of these transient intermediates.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, 1710 University Avenue, Madison, Wisconsin 53726, USA. reed@biochem.wisc.edu
authors.forename: George H
authors.initials: GH
authors.lastname: Reed
authors.forename: Steven O
authors.initials: SO
authors.lastname: Mansoorabadi
mesh_terms: D001665:Binding Sites; D003038:Cobamides / Q000737:chemistry*; D003067:Coenzymes / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D004789:Enzyme Activation; D004798:Enzymes / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D008958:Models, Molecular; D011485:Protein Binding; D013113:Spin Labels; D013379:Substrate Specificity
chemical_list: D003038:Cobamides; D003067:Coenzymes; D004798:Enzymes; D005609:Free Radicals; D013113:Spin Labels; C000913:cobamamide