Structural details of a calcium-induced molecular switch: X-ray crystallographic analysis of the calcium-saturated N-terminal domain of troponin C at 1.75 A resolution.
We have solved and refined the crystal and molecular structures of the calcium-saturated N-terminal domain of troponin C (TnC) to 1.75 A resolution. This has allowed for the first detailed analysis of the calcium binding sites of this molecular switch in the calcium-loaded state. The results provide support for the proposed binding order and qualitatively, for the affinity of calcium in the two regulatory calcium binding sites. Based on a comparison with the high-resolution apo-form of TnC we propose a possible mechanism for the calcium-mediated exposure of a large hydrophobic surface that is central to the initiation of muscle contraction within the cell.
Strynadka
N C
NC
Department of Biochemistry, University of Alberta, Edmonton, Canada.
Cherney
M
M
Sielecki
A R
AR
Li
M X
MX
Smillie
L B
LB
James
M N
MN
D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002645:Chickens; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D019209:Troponin C / Q000737:chemistry* / Q000378:metabolism; D014867:Water / Q000737:chemistry
D019209:Troponin C; D014867:Water; D002118:Calcium