title: Spin labeling studies of wheat germ calmodulin in solution.
abstract: Electron paramagnetic resonance was used to investigate the physical state of plant calmodulin in solution. Wheat germ calmodulin contains a single cysteine residue (Cys-27) on the first of four calcium binding loops. In this study the nitroxide spin label 2,2,6,6-tetramethyl-4-maleimidopiperidine-1-oxyl (MAL-6) was covalently attached to Cys-27 to produce a Ca(2+)-sensitive, biologically-active, labeled protein. The rotational correlation time of the spin label, a measure of its rotational mobility and reflective of the physical state of this region of the protein, was calculated under various conditions. Relative to control, changes in the physical state of the protein reflected by increased motion of the spin label were observed at high pH, low ionic strength and upon addition of Ca2+. These results extend knowledge of the structure of the protein, previously known from solid state and biochemical studies, to calmodulin in solution.
authors.affiliation: Department of Chemistry, University of Kentucky, Lexington 40506-0055.
authors.forename: M A
authors.initials: MA
authors.lastname: Yacko
authors.forename: T C
authors.initials: TC
authors.lastname: Vanaman
authors.forename: D A
authors.initials: DA
authors.lastname: Butterfield
mesh_terms: D002147:Calmodulin; D003497:Cyclic N-Oxides; D003545:Cysteine; D004578:Electron Spin Resonance Spectroscopy; D012996:Solutions; D013113:Spin Labels; D014909:Wheat Germ Agglutinins
chemical_list: D002147:Calmodulin; D003497:Cyclic N-Oxides; D012996:Solutions; D013113:Spin Labels; D014909:Wheat Germ Agglutinins; C017480:4-maleimido-2,2,6,6-tetramethylpiperidinooxyl; D003545:Cysteine