title: Thermal coefficients of the methyl groups within ubiquitin.
abstract: Physiological processes such as protein folding and molecular recognition are intricately linked to their dynamic signature, which is reflected in their thermal coefficient. In addition, the local conformational entropy is directly related to the degrees of freedom, which each residue possesses within its conformational space. Therefore, the temperature dependence of the local conformational entropy may provide insight into understanding how local dynamics may affect the stability of proteins. Here, we analyze the temperature dependence of internal methyl group dynamics derived from the cross-correlated relaxation between dipolar couplings of two CH bonds within ubiquitin. Spanning a temperature range from 275 to 308 K, internal methyl group dynamics tend to increase with increasing temperature, which translates to a general increase in local conformational entropy. With this data measured over multiple temperatures, the thermal coefficient of the methyl group order parameter, the characteristic thermal coefficient, and the local heat capacity were obtained. By analyzing the distribution of methyl group thermal coefficients within ubiquitin, we found that the N-terminal region has relatively high thermostability. These results indicate that methyl groups contribute quite appreciably to the total heat capacity of ubiquitin through the regulation of local conformational entropy.
authors.affiliation: Department of NMR-based Structural Biology, Max-Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany.
authors.forename: T Michael
authors.initials: TM
authors.lastname: Sabo
authors.forename: Davood
authors.initials: D
authors.lastname: Bakhtiari
authors.forename: Korvin F A
authors.initials: KF
authors.lastname: Walter
authors.forename: Robert L
authors.initials: RL
authors.lastname: McFeeters
authors.forename: Karin
authors.initials: K
authors.lastname: Giller
authors.forename: Stefan
authors.initials: S
authors.lastname: Becker
authors.forename: Christian
authors.initials: C
authors.lastname: Griesinger
authors.forename: Donghan
authors.initials: D
authors.lastname: Lee
mesh_terms: D002247:Carbon Isotopes / Q000737:chemistry; D019277:Entropy; D006801:Humans; D008745:Methylation; D056004:Molecular Dynamics Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D017510:Protein Folding; D055550:Protein Stability; D013696:Temperature; D013997:Time Factors; D025801:Ubiquitin / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D025801:Ubiquitin