Calcium-binding protein that modulates excitation-contraction coupling in the heart. Contributes to calcium homeostasis in the sarcoplasmic reticulum in the heart. Modulates the activity of RYR2 calcium channels. Homodimer. Interacts with GCA and RYR2 (By similarity). Interacts with ANXA7. Relocates to the sarcoplasmic reticulum membrane in response to elevated calcium levels and phosphorylation. Detected in myocardium. Phosphorylated; partially. This protein is encoded by an amplified gene in multidrug-resistant cells. This protein has been shown to bind calcium with high affinity.