Troponin C (TNC)

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Troponin C (TNC) together with TNI and TNT form the heterotrimer, troponin. It imparts calcium sensitivity to muscle. TNC has eleven residues in the linker; hence, the F2 _-helix, linker, E3 _-helix is eight turns long. TNC is dumbbell shaped in the apo form. The two lobes of TNC in the Ca4-form enfold the target peptide of TNI, residues 1-47, [8] in a conformation similar to the CAM*target complex. Most animals have several isoforms encoded at separate loci. In the dendrograms based on both protein and DNA the vertebrate skeletal and cardiac forms cluster separately indicating that the common precursor of all vertebrates already has these two isoforms. Halocynthia, a protochordate, has the most divergent TNC; its TNC clusters near the base of the cardiac branch (figure 4).