8.A.28.1.3
Triadin of 729 aas.  Contributes to the regulation of lumenal Ca²⁺ release via the sarcoplasmic reticulum calcium release channels RYR1 and RYR2, a key step in triggering skeletal and heart muscle contraction (Marty 2015). It is required for normal organization of the triad junction, where T-tubules and the sarcoplasmic reticulum terminal cisternae are in close contact. Triadin is required for normal skeletal muscle strength. It plays a role in excitation-contraction coupling in the heart and in regulating the rate of heart beats (Roux-Buisson et al. 2012). Triadin and junctin bind to different sites on RyR1; triadin plays an important role in ensuring rapid Ca²⁺ release during excitation-contraction coupling in skeletal muscle (Goonasekera et al. 2007). Althogh diffusible, a longer residence time in the ER-PM contact point is due to the transmembrane domain of T95 resulting in triad localization (Sébastien et al. 2020).