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

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