JSRP1: Proteins and Enzymes

The junction between the transverse tubules (T-tubules) and the sarcoplasmic reticulum (SR) of skeletal muscle is called the triad. At the triad, dihydropyridine receptors (DHPR®s) of the T-tubule serve as voltage sensors in excitation-contraction coupling, while ryanodine receptors (RyR®s), the calcium release channels, exist in the membrane of the terminal cisternae of the SR. It is thought that during slow phase depolarization of the T-tubule, a third protein, triadin (95 kDa) transmits electrochemical signals to the SR through direct interaction with both DHPR®s and RyR®s. Another skeletal muscle specific 90 kDa protein has also been localized to the this junction. This protein is phosphorylated by an intrinsic protein kinase in triads suggesting that it may play an important regulatory or structural role in the skeletal muscle triad junction.