Troponin is the central regulatory protein of striated muscle contraction. It consists of three components: Troponin-I (Tn-I) which is the inhibitor of actomyosin ATPase, Troponin-T (Tn-T) which contains the binding site for tropomyosin and Troponin-C (Tn-C). The binding of calcium to Tn-C abolishes the inhibitory action of Tn on actin filaments. Causes an allergic reaction in human. Binds to IgE in 14% of the 104 patients tested allergic to cockroach. Calcium depletion by 10 mM ethylene glycol bis(2-aminoethyl)tetraacetic acid (EGTA) does not significantly affect IgE-binding, but addition of 10 mM CaCl(2) after calcium depletion increases IgE-binding by approximately 2-fold. Belongs to the troponin C family.