Actin-binding proteins are conserved from slime molds to man.

DNA clones encoding the actin-binding proteins alpha-actinin and severin from Dictyostelium discoideum were isolated and sequenced. Comparisons of the deduced amino acid sequences with proteins from other species showed striking similarities at distinct regions. The F-actin cross-linking molecule alpha-actinin carries two characteristic EF-hand structures highly homologous to the Ca2+-binding loops of proteins from the calmodulin superfamily. An N-terminal region that is conserved in alpha-actinin from D. discoideum and vertebrates is also related to parts of the dystrophin sequence and might represent the F-actin binding site. Severin, gelsolin, villin, and fragmin share homologous sequences that are believed to participate in the severing activity of these proteins.