The reaction of myosin with N-ethylmaleimide in the presence of ADP |
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Authors: | JL Daniel DJ Hartshorne |
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Institution: | Departments of Biological Sciences and Chemistry, Carnegie-Mellon University, Pittsburgh, Pa. 15213 U.S.A. |
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Abstract: | Myosin reacted with N-ethylmaleimide in the presence of ADP lost its ability to be activated by actin. Subfragment 1 behaved similarly. About 2 moles of N-ethylmaleimide per mole of Subfragment 1 were required to eliminate actin activation of the Mg2+-ATPase activity. At the point at which actin activation was lost the K+-EDTA-ATPase activity was also lost, but the Ca2+-activated ATPase activity was increased. Kinetic measurements indicated that the labelling with N-ethylmaleimide in the presence of ADP reduced V (the ATPase activity at infinite actin concentration) but did not effect Kapp (which is related to the dissociation constant of the actin-Subfragment 1 complex). The Mg2+-activated activity of the reacted myosin alone remained unaltered and the ability to bind actin was retained. We propose that the N-ethylmaleimide labelling blocked the actin activation by preventing the accelerated release of hydrolysis products from the myosin. |
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Keywords: | EGTA 2 2′-ethylenedioxybis [ethyliminodi(acetic acid)] |
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