Calcium-binding protein that modulates excitation-contraction coupling in the heart. Contributes to calcium homeostasis in the heart sarcoplasmic reticulum. Modulates the activity of RYR2 calcium channels (By similarity). Homodimer. Interacts with GCA, RYR2 and ANXA7 (By similarity). Relocates to the sarcoplasmic reticulum membrane in response to elevated calcium levels. This protein has been shown to bind calcium with high affinity.