Figure 14.

Four-helix bundle formed by troponin-T and tropomyosin junction as determined by X-ray crystallography of the ternary complex of TM-C, TM-N and TnT.¹¹⁹⁾ Troponin-T and the tropomyosin junction formed an asymmetric four-helix bundle. The cylinder model is viewed from the M-line side. It also shows the “knob” (Leu-278 of TM-C), which is encircled, surrounded by hydrophobic side chains of Ile-4, Met-8, Leu-11, and the aliphatic part of Lys-7 of TM-N. The side chain of Phe-86 (cardiac Phe-110) of TnT faced against that of His-276 of TM-C (L-arm). This interaction is important to prevent the human cardiomyopathy.¹²³⁾