The effect of Mg ++ on the conformation of the Ca ++ -binding component of troponin |
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Authors: | Y Kawasaki J P Van Eerd |
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Institution: | 1. Department of Physics, Faculty of Science, Nagoya University, Nagoya, Japan 464.;2. Institute of Molecular Biology, Faculty of Science, Nagoya University, Nagoya, Japan 464. |
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Abstract: | Mg++ like Ca++ induces a conformational change in the Ca++-binding component of troponin. However, this change is only 36 % of the change in fluorescence intensity and 80 % of the change in optical rotation induced by Ca++. The apparent binding constant of Mg++ to the Ca++-binding component is 5 × 103 M?1, much smaller than that of Ca++. Circular dichroism measurements show that these changes are simple helix-coil transitions. Unlike the Ca++-induced conformational change, the Mg++-induced change cannot be propagated to other muscle proteins, and therefore has no physiological meaning. |
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