1. Archive
2. Vol.51, No.3

Effects of Sarcomere Length and Ca²⁺ Binding on H Reactivity of Myofilament Bound Troponin C in Porcine Skinned Cardiac Muscle Fibers

Abstract: Length dependence of cardiac Ca²⁺ activation is an essential component of the Frank-Starling relation. The aim of this study is to examine the length effects on the Ca²⁺-induced conformational changes of filament-bound cTnC in skinned cardiac muscle fibers. The two cysteine residues (Cys-35 and Cys-84) in the regulatory domain of cTnC allow for the attachment of conformational probes to this region. Their incorporation with the fluorescent probe, 7-diethylamino-3-[4′-maleimidylphenyl]-4-methylcoumarin (CPM), was used to determine the varying cTnC conformations in cardiac fibers. The data obtained show that the length-dependent Ca²⁺-mediated conformational changes require strong-binding cross-bridges for cardiac activation.

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