Distribution of tryptophan groups in molecules of troponin T, troponin I-troponin T complex, and alpha-actinin

The method of fluorescence quenching was used to experimentally determine the distribution of tryptophan residues in molecules of troponin T, troponin T-troponin I complexes, and alpha-actinin. Iodide and cesium ions, and acrylamide were used as quenchers. It was shown that cesium ions decrease the fluorescence intensity of troponin T and its complex with troponin I by the mode of dynamic quenching. For alpha-actinin such a dynamic quencher is anionic iodide. By using the modified Stern-Volmer equation, the quenching was found to be about 90% of total fluorescence intensity for troponin T, approximately 70% for the troponin T-troponin I complexes, and 20% for alpha-actinin. The penetration of cesium ions to tryptophan 206 (tryptophan 204) in the troponin T-troponin I complex is hindered, probably due to the participation of this tryptophan in the formation of bonds between troponin subunits.