Subnanometer Structure of the Actin/Myosin/Tropomyosin Complex

Abstract

Actins and myosins play a central role in life as they form the molecular motors that transform chemical energy into movement. Without them, we would be confined to a very static existence.To fully understand how the interplay between actin and myosin leads to the conversion of the energy stored in ATP into mechanical energy, one needs structural information. Therefore, we have set out to determine the complex structure of the three major muscle proteins (actin, myosin and tropomyosin) using cryo electron microscopy and iterative helical real-space reconstruction. Using state of the art instruments and reconstruction algorithms we have determined a sub-nanometer resolution electron density map of the complex. With the help of electron-density guided flexible fitting we have subsequently refined the structure to obtain a quasi-atomic resolution structure of the full complex which enabled us, for the first time, to visualize interactions between actin and myosin that have been postulated by computational methods beforehand. In addition, we could also identify a novel interaction between myosin and tropomyosin.