Crystal structure of the α-actinin rod reveals an extensive torsional twist

Background: alpha -Actinin is a ubiquitously expressed protein found in numerous actin structures. It consists of an N-terminal actin binding domain, a central rod domain, and a C-terminal domain and functions as a homodimer to cross-link actin filaments. The rod domain determines the distance between cross-linked actin filaments and also serves as an interaction site for several cytoskeletal and signaling proteins. Results: We report here the crystal structure of the alpha -actinin rod. The structure is a twisted antiparallel dimer that contains a conserved acidic surface. Conclusions: The novel features revealed by the structure allow prediction of the orientation of parallel and antiparallel cross-linked actin filaments in relation to alpha -actinin. The conserved acidic surface is a possible interaction site for several cytoplasmic tails of transmembrane proteins involved in the recruitment of alpha -actinin to the plasma membrane.