title: Determination of the individual roles of the linker residues in the interdomain motions of calmodulin using NMR chemical shifts.
abstract: Many protein molecules are formed by two or more domains whose structures and dynamics are closely related to their biological functions. It is thus important to develop methods to determine the structural properties of these multidomain proteins. Here, we characterize the interdomain motions in the calcium-bound state of calmodulin (Ca(2+)-CaM) using NMR chemical shifts as replica-averaged structural restraints in molecular dynamics simulations. We find that the conformational fluctuations of the interdomain linker, which are largely responsible for the overall interdomain motions of CaM, can be well described by exploiting the information provided by chemical shifts. We thus identify 10 residues in the interdomain linker region that change their conformations upon substrate binding. Five of these residues (Met76, Lys77, Thr79, Asp80 and Ser81) are highly flexible and cover the range of conformations observed in the substrate-bound state, while the remaining five (Arg74, Lys75, Asp78, Glu82 and Glu83) are much more rigid and do not populate conformations typical of the substrate-bound form. The ensemble of conformations representing the Ca(2+)-CaM state obtained in this study is in good agreement with residual dipolar coupling, paramagnetic resonance enhancement, small-angle X-ray scattering and fluorescence resonance energy transfer measurements, which were not used as restraints in the calculations. These results provide initial evidence that chemical shifts can be used to characterize the conformational fluctuations of multidomain proteins.
authors: Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK.
authors: Predrag
authors: P
authors: Kukic
authors: Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK.
authors: Carlo
authors: C
authors: Camilloni
authors: Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK.
authors: Andrea
authors: A
authors: Cavalli
authors: Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK. Electronic address: mv245@cam.ac.ukz.
authors: Michele
authors: M
authors: Vendruscolo
mesh_terms: D000818:Animals; D001665:Binding Sites; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D002147:Calmodulin; D029721:Drosophila Proteins
keywords: NMR spectroscopy; chemical shifts; molecular dynamics simulations; replica-averaged structural restraints