title: Changes in calmodulin main-chain dynamics upon ligand binding revealed by cross-correlated NMR relaxation measurements.
abstract: The fast dynamics of protein backbones are often investigated by nuclear magnetic relaxation experiments that report on the degree of spatial restriction of the amide bond vector. By comparing calmodulin in the peptide-bound and peptide-free states with these classical methods, we observe little difference in the dynamics of the polypeptide main chain (average order parameter decrease of 0.01 unit upon binding). However, when using NMR methods that monitor the mobility of the CO-Calpha bond vector, we reveal a significant reduction of dynamics of the protein main chain (average order parameter decrease of 0.048 units). Previous investigations have suggested that the side-chain dynamics is reduced by an average of 0.07 order parameter units upon ligand binding (Lee, A. L.; Kinnear, S. A.; Wand, A. J. Nat. Struct. Biol. 2000, 7, 72-77). The current findings suggest that the change of the CO-Calpha bond vector dynamics is intermediate between the changes in NH and side-chain dynamics and report a previously undetected loss of main-chain entropy. Weak site-to-site correlations between the different motional indicators are also observed.
authors.affiliation: Biophysics Research Division, Department of Biological Chemistry, The University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109-1055, USA.
authors.forename: Tianzhi
authors.initials: T
authors.lastname: Wang
authors.forename: Kendra King
authors.initials: KK
authors.lastname: Frederick
authors.forename: Tatyana I
authors.initials: TI
authors.lastname: Igumenova
authors.forename: A Joshua
authors.initials: AJ
authors.lastname: Wand
authors.forename: Erik R P
authors.initials: ER
authors.lastname: Zuiderweg
mesh_terms: D001665:Binding Sites; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism; D002247:Carbon Isotopes; D007700:Kinetics; D008024:Ligands; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013816:Thermodynamics
chemical_list: D002147:Calmodulin; D002247:Carbon Isotopes; D008024:Ligands; D010455:Peptides; C065738:MLCK peptide