Figure 5. Ca²⁺-saturated state structure of the cardiac troponin complex.

The cTn structure after 11.1²⁺-saturated state is depicted using CCP4MG version 2.7.3. (a) The secondary structure of the cTnI-Md and cTnI-Rr are conserved. The cTnI-Md points away from the cTn domain complex (b) The conformation of the helices B and C are almost orthogonal to each other. The helix D may be observed to have partially unfolded in this state. The structure of the N-terminal extension of cTnI above the cTn core domain complex is well seen. The N-extension of cTnI is seen interacting with sites 1 and 2 of cTnC. The C-terminus of cTnT is unfolded, probably an indication of its interaction with tropomyosin. The bound Ca²⁺ ions are seen as green dots. (c) Image of the cTnC N-domain as viewed from above the cTn complex. (d) The averaged structure of the cardiac troponin complex in the Ca²⁺ free state from 2 ns to 11.1 ns. The first two nanoseconds were given for the system to equilibrate.