Solution structure and main chain dynamics of the regulatory domain (Residues 1-91) of human cardiac troponin C.
The three-dimensional structure of calcium-loaded regulatory, i.e. N-terminal, domain (1-91) of human cardiac troponin C (cNTnC) was determined by NMR in water/trifluoroethanol (91:9 v/v) solution. The single-calcium-loaded cardiac regulatory domain is in a "closed" conformation with comparatively little exposed hydrophobic surface. Difference distance matrices computed from the families of Ca2+-cNTnC, the apo and two-calcium forms of the skeletal TnC (sNTnC) structures reveal similar relative orientations for the N, A, and D helices. The B and C helices are closer to the NAD framework in Ca2+-cNTnC and in apo-sNTnC than in 2.Ca2+-sNTnC. However, there is an indication of a conformational exchange based on broad 15N resonances for several amino acids measured at several temperatures. A majority of the amides in the alpha-helices and in the calcium binding loop exhibit very fast motions with comparatively small amplitudes according to the Lipari-Szabo model. A few residues at the N and C termini are flexible. Data were recorded from nonlabeled and 15N-labeled samples, and backbone dynamics was investigated by 15N T1, T2, and heteronuclear nuclear Overhauser effect as well as by relaxation interference measurements.
Pääkkönen
K
K
VTT, Chemical Technology, P. O. Box 1401 FIN-02044 VTT, Finland.
Annila
A
A
Sorsa
T
T
Pollesello
P
P
Tilgmann
C
C
Kilpeläinen
I
I
Karisola
P
P
Ulmanen
I
I
Drakenberg
T
T
D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009206:Myocardium / Q000737:chemistry*; D011487:Protein Conformation; D012996:Solutions; D019209:Troponin C / Q000737:chemistry*
D012996:Solutions; D019209:Troponin C; D002118:Calcium