Troponin I

**Semantic type:** Amino Acid, Peptide, or Protein

**Definition:** Troponin I, troponin T, and troponin C are the three closely associated subunits of the troponin complex of thin filaments in muscle. The complex serves as a calcium-sensitive switch that regulates muscle contraction. In the absence of calcium, Troponin I binds actin, inhibits actomyosin ATPase activity, and inhibits F-actin-myosin interactions. The troponin I gene family comprises three isoforms: skeletal TNI-fast, skeletal TNI-slow, and TNI-cardiac. (from OMIM 191044, 191043, 191042 and NCI)

**Synonyms:** - TNNI - TnI