Structure of the alpha-actinin rod: Molecular basis for cross-linking of actin filaments

We have determined the crystal structure of the two central repeats in the alpha-actinin rod at 2.5 Angstrom resolution. The repeats are connected by a helical linker and form a symmetric, antiparallel dimer in which the repe ats are aligned rather than staggered. Using this structure, which reveals the structural principle that governs the architecture of alpha-actinin, we have devised a plausible model of the entire alpha-actinin rod. The electr ostatic properties explain how the two alpha-actinin subunits assemble in a n antiparallel fashion, placing the actin-binding sites at both ends of the rod. This molecular architecture results in a protein that is able to form cross-links between actin filaments.