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

Background: alpha -Actinin is a ubiquitously expressed protein found in num erous 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 betwe en 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. Th e structure is a twisted antiparallel dimer that contains a conserved acidi c surface. Conclusions: The novel features revealed by the structure allow prediction of the orientation of parallel and antiparallel cross-linked actin filament s in relation to alpha -actinin. The conserved acidic surface is a possible interaction site for several cytoplasmic tails of transmembrane proteins i nvolved in the recruitment of alpha -actinin to the plasma membrane.