Gene superfamily: troponins C; (TNNC1 TNNC2)


In skeletal and cardiac muscle, the troponin C (TnC) is a Ca(2+)-binding subunit of the ternary troponin complex which, through its association with actin (FAM:ACT/00.0) and tropomyosin (see GEM:15q221/TPM1) on the thin filament, inhibits the interaction between actin and myosin (FAM:MY/00.0) at submicromolar Ca2+ concentrations and stimulates the interaction at micromolar Ca2+ concentrations (Farah-1995). Since TnC does not interact directly with actin or tropomyosin, the Ca(2+)-binding signal must be transmitted to the thin filament via the other two troponin subunits: troponin I (FAM:TNNI/00.0), the inhibitory subunit, and troponin T (FAM:TNNT/00.0), the tropomyosin-binding subunit."


The TNNC family belongs to the so named EF-hand homolog family which contains more than 160 different Ca(2+)-modulated proteins, i.e. calmodulin (see GEM:14q32/CALM1), myosin regulatory light chain (GEM:12q2/MYL2; GEM:04p163/MYL5), parvalbumin (GEM:22q1/PVALB), the S-100 proteins (FAM:S100A/01q21), calbindins 9 kDa (GEM:08q2/CALB1) and 28 kDa (GEM:0Xp222/CALB3), annexins (FAM:ANX/00.0) and others. The most striking feature of the EF-hand family is the ability to modulate the activity of a number of enzymes."


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