Site-1 Protease is a negative regulator of sarcolipin promoter activity.

The timed contraction and relaxation of myofibers in tissues such as the heart and skeletal muscle occurs via the tightly regulated movement of calcium ions into and out of the sarcoplasmic reticulum (SR). In skeletal muscle, this phenomenon enables humans to exercise, perform day-to-day tasks, and to breathe. Sarcolipin, a small regulatory protein, prevents calcium ions from entering the SR by binding to and inhibiting SERCA, contributing to myofiber contraction.