Fast skeletal troponin I (fsTnI) is a protein that plays a critical role in the regulation of muscle contraction in fast-twitch skeletal muscles. It is one of the three subunits that make up the troponin complex, which also includes troponin T and troponin C. The troponin complex works cooperatively with tropomyosin to regulate the interaction between actin and myosin filaments in muscle fibers.
