title: Exploring the Fe(III) binding sites of human serum transferrin with EPR at 275 GHz.
abstract: We report 275 GHz EPR spectra of human serum transferrin. At this high microwave frequency the zero-field splitting between the magnetic sublevels of the high-spin [Formula: see text] sites can be accurately determined. We find the zero-field splitting to be a sensitive probe of the structure of the transferrin iron-binding sites. Signals arising from iron bound to the transferrin N-lobe can clearly be distinguished from signals from iron bound to the C-lobe. Moreover, our spectra show that the structure of the iron site in the N-lobe is influenced by the presence and conformation of the C-lobe. The spectra of a series of N-lobe mutants altering the second-shell interaction of Arg124 with the synergistic anion carbonate reflect conformational changes induced at the iron site.
authors.affiliation: Department of Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, Leiden, The Netherlands, mathies@mit.edu.
authors.forename: Guinevere
authors.initials: G
authors.lastname: Mathies
authors.forename: Peter
authors.initials: P
authors.lastname: Gast
authors.forename: N Dennis
authors.initials: ND
authors.lastname: Chasteen
authors.forename: Ashley N
authors.initials: AN
authors.lastname: Luck
authors.forename: Anne B
authors.initials: AB
authors.lastname: Mason
authors.forename: Edgar J J
authors.initials: EJ
authors.lastname: Groenen
mesh_terms: D001665:Binding Sites; D001774:Blood Chemical Analysis; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D014168:Transferrin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D005290:Ferric Compounds; D014168:Transferrin