Conformations of the regulatory domain of cardiac troponin C examined by residual dipolar couplings.
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.
Pääkkönen
K
K
VTT Biotechnology, Helsinki, Finland.
Sorsa
T
T
Drakenberg
T
T
Pollesello
P
P
Tilgmann
C
C
Permi
P
P
Heikkinen
S
S
Kilpeläinen
I
I
Annila
A
A
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*
D019209:Troponin C; D019210:Troponin I