Small calcium binding protein that plays important roles in several biological processes such as Ca2+ homeostasis, chondrocyte biology and cardiomyocyte regulation. In response to an increase in intracellular Ca2+ levels, binds calcium which triggers conformational changes. These changes allow interactions with specific target proteins and modulate their activity. Regulates a network in cardiomyocytes controlling sarcoplasmic reticulum Ca2+ cycling and mitochondrial function through interaction with the ryanodine receptors RYR1 and RYR2, sarcoplasmic reticulum Ca2+-ATPase/ATP2A2 and mitochondrial F1-ATPase. Facilitates diastolic Ca2+ dissociation and myofilament mechanics in order to improve relaxation during diastole