Differences in internal dynamics of actin under different structural states detected by neutron scattering

Fujiwara, Satoru; Plazanet, M.*; Matsumoto, Fumiko; Oda, Toshiro*

Actin plays crucial roles in various aspects of cell motility. Flexibility of F-actin, a filamentous polymer formed by polymerization of the monomers (G-actin), is important for such a variety of functions. This flexibility allows F-actin to interact with various proteins, thereby expressing multiple functions. Understanding the variety of functions of actin thus requires understanding the flexibility of F-actin. As a first step towards this ultimate purpose, we carried out elastic incoherent neutron scattering (EINS) experiments on G-actin and F-actin under hydrated states. The mean square displacement (MSD) was estimated from the EINS measurements. Temperature dependence of MSD showed that two dynamical transitions occur at about 150 K and about 245 K, and that behavior of MSD is different between G-actin and F-actin, such that G-actin is "softer" than F-actin. The different behavior observed is ascribed to the differences in dynamical heterogeneity between F-actin and G-actin.