... volumes of 5M urea solution and then run on SDS ⁄ PAGE. Lanes a and d, in the absence of both TnC and Ca2+; lanes b and e, in the presence of TnC and the absence of Ca2+; lanes c and f, in the ... integrity of the tro-ponin complex. In molluskan muscles, the C-terminalregion does not function and troponin regulatescontraction only through the activation exerted by the N-terminal region of ... interaction in rabbitTnI–TnC in the absence of divalent cation. Therefore,this interaction potentially participates in both the Ca2+-dependent activation of the contraction and the maintenance of...