Figure 3. Selective deletion of the NH₂-terminal variable region from TnT does not abolish binding to Tm.

Solid-phase protein binding curves of intact mouse cardiac TnT, McTnT-ND₇₂ and McTnT-ND₉₁ to Tm demonstrate the effect of TnT NH₂-terminal truncations. The binding affinity of McTnT-ND₇₂ to Tm was similar to that of the intact McTnT while the Tm binding affinity of McTnT-ND₉₁ was decreased (P<0.001). There was no significant change in the maximal binding of McTnT-ND₇₂ and McTnT-ND₉₁ to Tm (inset). In contrast to the preserved activity of McTnT-ND₇₂ with only the NH₂-terminal variable region deleted, the decreased binding of McTnT-ND₉₁ to Tm indicates that deletion into the conserved region damages the TnT core structure by disrupting the central Tm binding site (Fig. 1).