Structure of the calcium regulatory muscle protein troponin-C at 2.8 Å resolution

Abstract
Crystals of turkey skeletal muscle troponin-C reveal a molecule of 2 domains with an unusual structure. Two Ca2+ ions are bound to the C-terminal domain. The 2 cation-binding sites of the regulatory (N-terminal) domain are Ca2+ free; this domain adopts a markedly different conformation from the C-terminal domain. The 2 domains are connected by a long 9-turn .alpha.-helix; 3 of these turns are exposed fully to solvent.