title: A 13C labeling strategy reveals a range of aromatic side chain motion in calmodulin.
abstract: NMR relaxation experiments often require site-specific isotopic enrichment schemes in order to allow for quantitative interpretation. Here we describe a new labeling scheme for site-specific (13)C-(1)H enrichment of a single ortho position of aromatic amino acid side chains in an otherwise perdeuterated background by employing a combination of [4-(13)C]erythrose and deuterated pyruvate during growth on deuterium oxide. This labeling scheme largely eliminates undesired contributions to (13)C relaxation and greatly simplifies the fitting of relaxation data using the Lipari-Szabo model-free formalism. This approach is illustrated with calcium-saturated vertebrate calmodulin and oxidized flavodoxin from Cyanobacterium anabaena . Analysis of (13)C relaxation in the aromatic groups of calcium-saturated calmodulin indicates a wide range of motion in the subnanosecond time regime.
authors.affiliation: Graduate Group in Biochemistry and Molecular Biophysics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Vignesh
authors.initials: V
authors.lastname: Kasinath
authors.forename: Kathleen G
authors.initials: KG
authors.lastname: Valentine
authors.forename: A Joshua
authors.initials: AJ
authors.lastname: Wand
mesh_terms: D002147:Calmodulin / Q000737:chemistry*; D002247:Carbon Isotopes; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009038:Motion
chemical_list: D002147:Calmodulin; D002247:Carbon Isotopes; D006841:Hydrocarbons, Aromatic