Kinetics of the Conformational Change of Troponin-C Induced by Magnesium-Binding or Removal

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Abstract
The kinetics of the conformational change of troponin-C (TN-C) induced by magnesiumbinding or removal were studied in the absence of calcium ion by measuring the fluorescence intensity change of BIPM bound to TN-C by stopped-flow spectrofluorometry. The kinetic process of the conformational change was biphasic. The rate constants of the two phases were determined as a function of free magnesium ion concentration ([Mg]) of the solution. The of the rate constants was explained by a simple molecular kinetic mechanism: The dissociation constant of magnesium bound to TN-C was also determined to be 1 × 10−2 M in the kinetic study.