Actin filaments are protein fibers that make up the internal skeleton of the cell. As active elements of our cells, actin filaments support the cell's fusion, movement and are involved in many other cellular processes. Importantly, they are also a major constituent of muscle cells. The structural complexity of these filaments has fascinated scientists since its discovery in the 1940s -- and has opened a sea of unanswered questions behind their ability to facilitate many processes of the cell. For the first time, researchers have been successfully able to visualize hundreds of water molecules in the actin filament, representing a quantum leap in actin research. Using the technique of electron cryo microscopy (cryo-EM), scientists reveal in unprecedented detail how actin proteins are arranged together in a filament, how ATP -- the cell's energy source -- sits in the protein pocket, and where individual water molecules position themselves and react with ATP.
