title: Temperature dependence of fast dynamics in proteins.
abstract: The temperature dependence of the internal dynamics of recombinant human ubiquitin has been measured using solution NMR relaxation techniques. Nitrogen-15 relaxation has been employed to obtain a measure of the amplitude of subnanosecond motion at amide N-H sites in the protein. Deuterium relaxation has been used to obtain a measure of the amplitude of motion of methyl-groups in amino-acid side chains. Data was obtained between 5 and 55 degrees C. The majority of amide N-H and methyl groups show a roughly linear (R(2)>0.75) temperature dependence of the associated Lipari-Szabo model-free squared generalized-order parameter (O(2)) describing the amplitude of motion. Interestingly, for those sites showing a linear response, the temperature dependence of the backbone is distinct from that of the methyl-bearing side chains with the former being characterized by a significantly larger Lambda-value, where Lambda is defined as d ln(1 - O)/d lnT. These results are comparable to the sole previous such study of the temperature dependence of protein motion obtained for a calmodulin-peptide complex. This suggests that the distinction between the main chain and methyl-bearing side chains may be general. Insight into the temperature dependence is gathered from a simple two-state step potential model.
authors.forename: Xiang-jin
authors.initials: XJ
authors.lastname: Song
authors.forename: Peter F
authors.initials: PF
authors.lastname: Flynn
authors.forename: Kim A
authors.initials: KA
authors.lastname: Sharp
authors.forename: A Joshua
authors.initials: AJ
authors.lastname: Wand
mesh_terms: D003198:Computer Simulation; D006801:Humans; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D009038:Motion; D011487:Protein Conformation; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000737:chemistry / Q000648:ultrastructure; D025801:Ubiquitin / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure*
chemical_list: D011994:Recombinant Proteins; D025801:Ubiquitin