Stepwise C-Terminal Truncation of Cardiac Troponin T Alters Function at Low and Saturating Ca2+

Activation of striated muscle contraction occurs in response to Ca2+ binding to troponin C (TnC). The resulting reorganization of troponin repositions tropomyosin on actin and permits activation of myosin catalyzed ATP hydrolysis. It now appears that the C-terminal 14 amino acids of cardiac troponin T (TnT) control the level of activity at both low and high Ca2+. We made a series of C-terminal truncation mutants of human cardiac troponin T, isoform 2, to determine if the same residues of TnT are involved in the low and high Ca2+ effects.

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