Antibodies against invertebrate actin: Their phylogenetic cross‐reactivity

Invertebrate muscle actin was extracted from penaeid shrimp tail muscle and purified by self‐assembly polymerization. Further purification for use as an antigen was accomplished by SDS polyacrylamide gel electrophoresis. Antibodies to highly purified shrimp tail muscle actin were produced in rabbits and were collected as an ammonium sulfate gamma globulin fraction from sera. These antibodies, which cross react with native actin, SDS denatured actin, and formalin fixed actin were successfully used to immunofluorescently label actin in cells. Actin in muscle and non‐muscle cell types from species of five invertebrate phyla and numerous species of vertebrates were labeled with no apparent difference in antibody specificity or sensitivity. These results suggest that the immune identity of the actin molecule is conserved over the span of the phylogenetic tree.