Troponin T is the tropomyosin-binding subunit of troponin, the thin filament regulatory complex which confers calcium-sensitivity to striated muscle actomyosin ATPase activity. Additional isoforms seem to exist. Isoforms A1e17, A2e17, A3e17, A4e17, A5e17 and A6e17 are acidic while isoforms B1e16, B2e17, B2e16, B3e17, B3e16, B4e17 and B4e16 are basic. Expressed predominantly in skeletal muscle. Embryo and neonate express predominantly acidic isoforms while all adult isoforms are basic. Only one isoform, B2e17, is found in both embryo/neonate and adult. A transition from high to low molecular weight isoforms is also seen during postnatal development. Belongs to the troponin T family.