Figure 3.

Structural and functional domains of cardiac TnT, alternative spliced exons, and posttranslational modifications. Outlined on this linear map of cardiac TnT polypeptide (residue #s are those published in the original papers, which used various isoforms from different species), the functional segments T1, T2, and the N-terminal hypervariable region as well as the alternatively spliced exons 4, 5, and 13 are indicated. Ser₂ is a highly conserved residue constitutively and phosphorylated in cardiac TnT in vivo (Perry, 1998; Sancho Solis et al., 2008). In vitro studies demonstrated that cardiac TnT could be phosphorylated by PKC at Thr₁₉₇, Ser₂₀₁, Thr₂₀₆, and Thr₂₈₇ in the C-terminal region that contains binding sites for TnI, TnC, and tropomyosin (Jideama et al., 1996). Thr₂₀₆ can also be phosphorylated by Raf-1 (Pfleiderer et al., 2009) and Ser₂₇₈ and Thr₂₈₇ by ROCK2, which inhibited tension development and ATPase activity in skinned fibers (Vahebi et al., 2005). Thr₁₉₄ and Ser₁₉₈ of cardiac TnT have been found to be phosphorylated by ASK1 with decreases in cardiomyocyte contractility (He et al., 2003).