The kinetics of the exchange of G-actin-bound 1: N6-ethenoadenosine 5'-triphosphate with ATP as followed by fluorescence.
1: N6-Ethenoadenosine 5'-triphosphate (epsilonATP), a fluorescent analog of ATP, binds to monomeric actin with a binding constant which is only about 5 times smaller than that of ATP. The spectroscopic changes which occur when epsilonATP binds to actin are studied and used to monitor the kinetics of nucleotide exchange. The first-order rate constant which is measured at a large excess of ATP over epsilonATP strongly depends on the ATP and Ca+ concentrations. This finding is explained by a mechanism in which the nucleotide dissociates much more easily from Ca2+-free than from Ca2+-bound actin. Of special interest is the temperature dependence of the dissociation rate constant. The Arrhenius plot shows a sharp bend near 24 degrees C.
D000199:Actins; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives*; D000818:Animals; D001665:Binding Sites; D002118:Calcium; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008433:Mathematics; D009132:Muscles / Q000032:analysis; D011485:Protein Binding; D011817:Rabbits; D013050:Spectrometry, Fluorescence
D000199:Actins; D000255:Adenosine Triphosphate; D002118:Calcium