9-anthroylnitrile binding to serine-181 in myosin subfragment 1 as revealed by FRET spectroscopy and molecular modeling

It has been shown that one of the 12 serine residues within the 23 kDa segm ent of myosin subfragment I can be covalently modified with a fluorescent p robe 9-anthroylnitrile (ANN) [Hiratsuka, T. (1989) J. Biol. Chem. 264 (30), 18188-18194]. To identify the exact binding site of the probe, the distanc es between the bound ANN as donor and acceptors in known positions (Lys-553 or Cys-707) of the myosin head were determined by using fluorescence reson ance energy transfer. Comparison of the spectroscopic results with distance s obtained from the atomic model of subfragment 1 revealed that ANN binds t o Ser-181. The result was in good agreement with the assumptions of Andreev and co-workers [Andreev, O. A., et al. (1995) J. Muscle Res. Cell Motil. 1 6 (4), 353-367]. This conclusion was further supported by protein modeling calculations. The results presented herein might bring ANN into the focus w hen the molecular mechanism and effects of the binding of ATP and its subse quent hydrolysis are studied.