NMR solution structure of calcium-saturated skeletal muscle troponin C.

摘要: Troponin C (TnC) is an 18 kDa (162-residue) thin-filament calcium-binding protein responsible for triggering muscle contraction upon the release of calcium from sarcoplasmic reticulum. The structure TnC with two ions bound has previously been solved by X-ray methods. Shown here solution which using 3D and 4D heteronuclear nuclear magnetic resonance (NMR) spectroscopic techniques. 1H, 13C, 15N backbone chemical shifts have already published [Slupsky, C. M., Reinach, F. C., Smillie, L. B., & Sykes, B. D. (1995) Protein Sci. 4, 1279-1290]. Presented herein are side-chain 80% complete. calcium-saturated was determined on basis 2106 NOE-derived distance restraints, 121 phi dihedral angle 76 psi restraints. appearance reveals a dumbbell-shaped molecule globular domains connected linker. structures N-terminal C-terminal highly converged [backbone atomic root mean square deviations (rmsd) about coordinate position residues 10-80 98-155 0.66 +/- 0.17 0.69 0.18 A, respectively]; however, orientation one domain respect to other not well-defined, thus each appears be structurally independent. Comparison form half-saturated methods major differences. First, there structural change occurs in resulting opening hydrophobic pocket presumably present itself its target troponin I. This involve only helices B move away N/A/D alteration phi, angles glutamic acid 41 irregular crystal (-97 degrees, -7 degrees) helical NMR (-60 -34 degrees). difference between presence flexible linker structure. allows adopt any another such that they can interact variety targets.