Chalovich, JosephChen, Yi-DerDudek, Ronald W.Hai, Luo2010-11-082011-05-172010-11-082011-05-171995-04-28Journal of Biological Chemistry; 270:17 p. 9911-9916http://hdl.handle.net/10342/2994The time course of interaction of caldesmon with actin may be monitored by fluorescence changes that occur upon the binding of 12-(N-methyl-N-(7-nitrobenz-2-oxa-l,3-diazol-4-yl))-labeled caldesmon to actin or to acrylodan actin. The concentration dependence of the observed rate of caldesmon-actin binding was analyzed to a first approximation as a single-step reaction using a Monte Carlo simulation. The derived association and dissociation rates were 107 M-1 s-1 and 18.2 s-1, respectively. Smooth muscle tropomyosin enhances the binding of caldesmon to actin, and this was found to be due to a reduction in the rate of dissociation to 6.3 s -1. There is no evidence from this study for a different mechanism of binding in the presence of tropomyosin. The fluorescence changes that occurred with the binding of 12-(N-methyl-N-(7-nitrobenz-2-oxa-l,3-diazol-4-yl))-labeled caldesmon to actin or actin-tropomyosin were reversed by the addition of myosin subfragment 1 as predicted by a competitive binding mechanism. Originally published in the Journal of Biological Chemistry, Vol. 270, No. 17, 1995.en-USPermission granted by author to Kent Nixon Myers to upload this article on 10/03/2010.Caldesmon interactionsFlourescence changes in labeled moleculesActin bindingArticlePMC126263310.1074/jbc.270.17.9911