The troponin complex associates with tropomyosin (Tm1) and controls the contraction of the striated muscle in response to changes in intracellular calcium concentration. The troponin-I subunit isoforms are encoded by a single gene, wupA. In the absence of a calcium ion stimulus, troponin-I binds to actin in thin myofilaments inhibiting the movement of tropomyosin from the myosin-binding sites. (Adapted from FBrf0226138 and PMID:31448287.)