HRC is a 699 amino acid that binds low-density lipoprotein with high affinity. As a high capacity calcium binding protein, HRC regulates the sequestration and release of calcium in the lumen of the junctional sarcoplasmic reticulum (SR) of cardiac, skeletal and smooth muscle. This mechanism may involve direct interaction between HRC and the cytoplasmic domain of Triadin, an integral membrane protein of the SR. The gene encoding HRC maps to human chromosome 19q13.33 and mouse chromosome 7 B4