title: Site-directed methyl group labeling as an NMR probe of structure and dynamics in supramolecular protein systems: applications to the proteasome and to the ClpP protease.
abstract: Methyl groups are powerful reporters of structure, motion, and function in NMR studies of supramolecular protein assemblies. Their utility can be hindered, however, by spectral overlap, difficulties with assignment or lack of probes in biologically important regions of the molecule studied. Here we show that (13)CH(3)-S- labeling of Cys side chains using (13)C-methyl-methanethiosulfonate ((13)C-MMTS) (IUPAC name: methylsulfonylsulfanylmethane) provides a convenient probe of molecular structure and dynamics. The methodology is demonstrated with an application focusing on the gating residues of the Thermoplasma acidophilum proteasome, where it is shown that the (13)CH(3)-S- label reports faithfully on the conformational heterogeneity and dynamics in this region of the complex. A second and related application involves labeling with (13)C-MMTS at the N-termini of the subunits comprising the E. coli ClpP protease that reveals multiple conformations of gating residues in this complex as well. These N-terminal residues adopt a single conformation upon gate opening.
authors.affiliation: Department of Molecular Genetics, The University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Tomasz L
authors.initials: TL
authors.lastname: Religa
authors.forename: Amy M
authors.initials: AM
authors.lastname: Ruschak
authors.forename: Rina
authors.initials: R
authors.lastname: Rosenzweig
authors.forename: Lewis E
authors.initials: LE
authors.lastname: Kay
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D049071:Endopeptidase Clp / Q000737:chemistry* / Q000378:metabolism*; D010450:Endopeptidases / Q000737:chemistry* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011487:Protein Conformation; D013194:Staining and Labeling
chemical_list: D019843:Archaeal Proteins; D029968:Escherichia coli Proteins; D010450:Endopeptidases; C483572:ClpP protease, E coli; D049071:Endopeptidase Clp; C093138:proteasome, Thermoplasma