Key result
The length-induced increase in Ca2+ sensitivity was greater with cardiac TnC than fast skeletal TnC, and modifying site 1 of cardiac TnC to bind a 4th Ca2+ ion suppressed this length dependence.
Cardiac troponin C, specifically its metal ion binding properties at site 1, plays a specialized role in modulating the length dependence of Ca2+ sensitivity in the myocardium.
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TnC site 1 properties may modulate myocardial length dependence; leaves open translation beyond animal models.
Gulati et al. (1991) studied this question. Troponin C (TnC) exchange and recombinant mutants (CBM1, CBM2A) vs. Fast skeletal TnC / native TnC was evaluated on Length dependence of Ca2+-sensitive force (pCa-force relationship). The length-induced increase in Ca2+ sensitivity was greater with cardiac TnC than fast skeletal TnC, and modifying site 1 of cardiac TnC to bind a 4th Ca2+ ion suppressed this length dependence.
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