Destabilizing tropomyosin-troponin I interactions increases calcium sensitivity

Abstract

The cardiac thin filament (TF), containing troponin (Tn) and tropomyosin (Tpm) bound to filamentous actin, is the main transducer that relates sarcoplasmic calcium levels to the contraction-relaxation cycles of the myocardium. In the absence of calcium, Tn interactions with Tpm inhibit actomyosin interactions. Calcium binding to TnC induces a shift in Tpm position along thin filaments, allowing for heart muscle contraction. While much of the TF structure has been well characterized, important regions of the communication pathway where Tn triggers Tpm movement remain unresolved.