The crystal structure of uncomplexed actin in the ADP state

The dynamics and polarity of actin filaments are controlled by a conformati onal change coupled to the hydrolysis of adenosine S'-triphosphate (ATP) by a mechanism that remains to be elucidated. Actin modified to block polymer ization was crystallized in the adenosine 5'-diphosphate (ADP) state, and t he structure was solved to 1.54 angstrom resolution. Compared with previous ATP-actin structures from complexes with deoxyribonuclease I, profilin, an d gelsotin, monomeric ADP-actin is characterized by a marked conformational change in subdomain 2. The successful crystallization of monomeric actin o pens the way to future structure determinations of actin complexes with act in-binding proteins such as myosin.