title: Conformational selection and functional dynamics of calmodulin: a (19)F nuclear magnetic resonance study.
abstract: Calcium-bound calmodulin (CaM-4Ca(2+)) is innately promiscuous with regard to its protein interaction network within the cell. A key facet of the interaction process involves conformational selection. In the absence of a binding peptide, CaM-4Ca(2+) adopts an equilibrium between a native state (N) and a weakly populated near-native peptide-bound-like state (I), whose lifetime is on the order of 1.5 ms at 37 °C, based on (19)F nuclear magnetic resonance (NMR) Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion measurements. This peptide-bound-like state of CaM-4Ca(2+) is entropically stabilized (ΔS = 280 ± 35 J mol(-1) K(-1)) relative to the native state, water-depleted, and likely parental to specific bound states. Solvent depletion, conformational selection, and flexibility of the peptide-bound-like state may be important in priming the protein for binding. At higher temperatures, the exchange rate, kex, appears to markedly slow, suggesting the onset of misfolded or off-pathway states, which retards interconversion between N and I. (19)F NMR CPMG relaxation dispersion experiments with both CaM-4Ca(2+) and the separate N-terminal and C-terminal domains reveal the cooperative role of the two domains in the binding process and the flexibility of the N-terminal domain in facilitating binding. Thus, when calcium binds, calmodulin establishes its interaction with a multitude of protein binding partners, through a combination of conformational selection to a state that is parental to the peptide-bound state and, finally, induced fit.
authors.affiliation: Department of Chemistry, University of Toronto, UTM , 3359 Mississauga Road North, Mississauga, ON L5L 1C6, Canada.
authors.forename: Joshua
authors.initials: J
authors.lastname: Hoang
authors.forename: R Scott
authors.initials: RS
authors.lastname: Prosser
mesh_terms: D002147:Calmodulin / Q000737:chemistry*; D005461:Fluorine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011487:Protein Conformation
chemical_list: D002147:Calmodulin; D005461:Fluorine