Involved in skeletal muscle excitation/contraction coupling (EC), probably acting as a regulator of the voltage-sensitive calcium channel CACNA1S. EC is a physiological process whereby an electrical signal (depolarization of the plasma membrane) is converted into a chemical signal, a calcium gradient, by the opening of ryanodine receptor calcium release channels. May regulate CACNA1S membrane targeting and activity. Interacts with CACNA1S, CACNB1 and calsequestrin. Colocalizes with ryanodine receptors at the sarcoplasmic reticulum triad membranes. It is uncertain whether Met-1 or Met-3 is the initiator.