The NMR angle on troponin C

The calcium-induced structural changes in the skeletal muscle regulatory pr otein troponin C involve a transition from a closed to an open structure wi th the concomitant exposure of a large hydrophobic interaction site for tar get proteins. NMR solution structural studies have served to define this co nformational change and elucidate the mechanism of the linkage between calc ium binding and the induced structural changes. These structural movements an described in terms of interhelical angles in these largely helical prote ins. Oddly, the most recent structure of the cardiac system challenges the central paradigm because the calcium-bound structures are not open. The kin etics, energetics, and dynamics of these proteins have also been investigat ed using NMR.