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Description

Troponin I, cardiac muscle (UniProt: P19429, also known as Cardiac troponin I) is encoded by the TNNI3 (also known as TNNC1) gene (Gene ID: 7137) in human. Troponin is a complex that regulates the contraction of skeletal muscle, It consists of 3 subunits known as C, T, and I, which are located periodically along the thin filament of the myofibrils. Troponin C (TnC) binds calcium ions, Troponin I is the inhibitory subunit of troponin that inhibits actomyosin ATPase and Troponin T binds to tropomyosin. It also confers calcium-sensitivity to actomyosin ATPase. Amino acids region 32-79 of Troponin I is involved in binding to TnC and region 129-149 is involved in binding to both TnC and actin. It is thought that troponin I acts as a switch, by moving away from actin toward troponin C, following Ca2+ binding to TnC. Cardiac muscle Troponin I has 31 amino acid residues on its N-terminal that are not present in the skeletal muscle form. Hence, cardiac specificity of this isoform is shown to offer accuracy in diagnosis in patients with acute or chronic skeletal muscle injury. Mutation in TNNI3 gene are reported to result in multiple types of cardiomyopathies that can result in premature death. (Ref.: Li, H-C., and Fajer, PG (1998). Biochemistry 37(19), 6628-6635).