Human cardiac troponin T amino terminus is required for inhibition and cooperative activation of Ca2+-dependent thin filament sliding

Abstract

The most N-terminal “tail” portion of the troponin T (TnT) subunit has received less attention than the rest of troponin (Tn) and has not yet been resolved in X-ray structures of Tn or cryo-EM structures of the cardiac thin filament. Existing cryo-EM structures of cardiac thin filaments show, in diastole (low Ca2+), the TnT tail extends one way from Tn core domain, and the C-terminus of troponin I (TnI) extends in the other direction. Functionally, N-terminal tail peptide of either skeletal or cardiac TnT inhibits actomyosin in the absence of the rest of Tn.