Conformation change in reconstituted thin filament studied with fluorescence energy transfer between epsilon-ADP bound to F-actin and NBD-Cl bound to troponin-C.

The interaction of troponin and F-actin was studied by the methods of fluorescence energy transfer. We used epsilon-ADP bound to F-actin as a fluorescence donor and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole bound to troponin-C in troponin as a fluorescence acceptor. The efficiency of the fluorescence energy transfer of this system was larger in the absence of calcium ion than in the presence of calcium ion. This shows that the interaction of troponin with F-actin changes in response to the concentration of calcium ion.