title: Characterization of threonine side chain dynamics in an antifreeze protein using natural abundance 13C NMR spectroscopy.
abstract: The dynamics of threonine side chains of the Tenebrio molitor antifreeze protein (TmAFP) were investigated using natural abundance (13)C NMR. In TmAFP, the array of threonine residues on one face of the protein is responsible for conferring its ability to bind crystalline ice and inhibit its growth. Heteronuclear longitudinal and transverse relaxation rates and the [(1)H]-(13)C NOE were determined in this study. The C alpha H relaxation measurements were compared to the previously measured (15)N backbone parameters and these are found to be in agreement. For the analysis of the threonine side chain motions, the model of restricted rotational diffusion about the chi(1) dihedral angle was employed [London and Avitabile (1978) J. Am. Chem. Soc., 100, 7159-7165]. We demonstrate that the motion experienced by the ice binding threonine side chains is highly restricted, with an approximate upper limit of less than +/-25 degrees.
authors.affiliation: Department of Biochemistry, CIHR Group in Protein Structure and Function and Protein Engineering Network of Centres of Excellence, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Daley
authors.forename: Brian D
authors.initials: BD
authors.lastname: Sykes
mesh_terms: D000818:Animals; D021301:Antifreeze Proteins / Q000737:chemistry*; D002247:Carbon Isotopes / Q000737:chemistry; D003198:Computer Simulation; D019476:Insect Proteins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D011487:Protein Conformation; D013712:Tenebrio / Q000378:metabolism; D013912:Threonine / Q000737:chemistry*
chemical_list: D021301:Antifreeze Proteins; D002247:Carbon Isotopes; D019476:Insect Proteins; D013912:Threonine