Sarcolipin (SLN) is a 3 kD membrane protein found in sarcoplasmic reticulum (SR). It has 31 amino acid residues; SLN and phopholamban (PLB) are belong to the same protein family, so they have similar physiological functions. SLN inhibits sarcoplasmic reticulum Ca(2+) ATPase (SERCA) activity and reduces its affinity of Ca(2+), resulting in dysfunction of myocardial contraction and heart failure.