The effect of troponin C removal on the Ca2+-sensitive binding of Mg2+ AMPPNP to myofibrils.
It was previously shown that when rabbit skeletal myofibrils are titrated with Mg2+ AMPPNP under conditions that result in the dissociation of cross-bridges from the thin filaments (i.e. 50% ethylene glycol, 0 degrees C), Ca2+-sensitive, biphasic binding is observed. These titrations have been repeated using myofibrils from which the troponin C has been selectively removed. The disappearance of both Ca2+ sensitivity and biphasic binding is taken as evidence that the Ca2+ sensitivity is due to Ca2+ binding to troponin C and the biphasic binding of Mg2+ AMPPNP observed in intact myofibrils is not due to packing constraints or steric hindrance.
Johnson
R E
RE
University Department of Biochemistry, University of Arizona, Tucson 85721.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D009210:Myofibrils / Q000187:drug effects / Q000378:metabolism*; D011817:Rabbits; D014336:Troponin / Q000502:physiology*; D019209:Troponin C
D014336:Troponin; D019209:Troponin C; D002118:Calcium