Comparative study of invertebrate actins: antigenic cross-reactivity versus sequence variability.

The immunological similarities or differences between various actins from muscles of invertebrates were investigated. We elicited antibodies to actin purified from the adductor muscle of the mollusc, Pecten maximus. The antiserum comprised a major population that was specific for the N-terminal extremity of this isoform. This antibody population was used together with other antibodies specific for various domains on the surface of skeletal muscle actin to compare seven actins from invertebrate muscles. The N-terminal extremity showed close homologies between invertebrates (except for Crustacea) but differences were observed with vertebrate skeletal and cytoplasmic actins. In contrast, sequence 18-28, which constitutes part of the myosin interaction domain, appears to be conserved in all actins studied. Other regions (sequences 40-113, 168-226 and 285-375) presented a variable behaviour depending on the particular invertebrate species.