title: Conformations of the regulatory domain of cardiac troponin C examined by residual dipolar couplings.
abstract: Conformations of the regulatory domain of cardiac troponin C (cNTnC) were studied by means of residual dipolar couplings measured from samples dissolved in dilute liquid crystals. Changes in the main chain HN residual dipolar couplings revealed a conformational change in cNTnC due to the complexation with the second binding region (amino acids 148-163) of cardiac troponin I (cTnI). Formation of the complex is accompanied with a molecular realignment in the liquid crystal. The residual dipolar couplings measured for apo-cNTnC and the complex with TnI were in agreement with the values computed from the corresponding closed and open solution structures, whereas for the calcium-loaded conformation the correlation and quality factor were only modest. Ca2+-cNTnC may be subject to conformational exchange. The data support the model that cardiac troponin C functions as a calcium-dependent open-closed switch, such as the skeletal troponin C.
authors.affiliation: VTT Biotechnology, Helsinki, Finland.
authors.forename: K
authors.initials: K
authors.lastname: Pääkkönen
authors.forename: T
authors.initials: T
authors.lastname: Sorsa
authors.forename: T
authors.initials: T
authors.lastname: Drakenberg
authors.forename: P
authors.initials: P
authors.lastname: Pollesello
authors.forename: C
authors.initials: C
authors.lastname: Tilgmann
authors.forename: P
authors.initials: P
authors.lastname: Permi
authors.forename: S
authors.initials: S
authors.lastname: Heikkinen
authors.forename: I
authors.initials: I
authors.lastname: Kilpeläinen
authors.forename: A
authors.initials: A
authors.lastname: Annila
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D008958:Models, Molecular; D018482:Muscle, Skeletal; D009206:Myocardium; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D019209:Troponin C / Q000737:chemistry*; D019210:Troponin I / Q000737:chemistry*
chemical_list: D019209:Troponin C; D019210:Troponin I