Sorcin is a 198aa, soluble, resistance-related, calcium-binding cytosolic protein belonging to the penta-EF hand (PEF) family of calcium binding proteins and contains 4 EF-hand calcium-binding motifs. Human Sorcin is known to share 95% sequence identity with hamster Sorcin. It is known to associate with the sarcolemmal proteins Annexin VII, cardiac ryanodine receptors and L-type Ca2+ channels and thus influence the intracellular Ca (2+)-homeostasis. It is also important in the regulation of intracellular Ca2+ cycling and Ca2+ influx pathways in the heart and skeletal muscle during excitation-contraction. It is overproduced in many multi-drug resistance (MDR) cells and regulates cell apoptosis pathways, thus acting as a new MDR marker for prognosis of acute myeloid leukemia (AML) and a good target for anti-MDR drug development.