Tubulins from different higher plant species are immunologically nonidentical and bind colchicine differentially.
We have initiated immunological and drug-binding studies on the tubulins from different higher plant species. Antibodies were raised against electrophoretically separated rose (Rosa sp.) tubulin alpha- and beta-subunits and characterized by immunoblot autoradiographic assays. Each IgG preparation bound to its antigen and cross-reacted differentially with the respective tubulin subunits from an alga, sea urchin, rabbit, and cow. Antigenic determinants were shared more among the beta-subunits than among the alpha-subunits from these organisms. Tubulins were isolated from cultured cells of carrot (Daucus carota) and hibiscus (Hibiscus rosa-senensis). Immunoautoradiography and quantitation of cross-reactivity on blots showed nonidentity among homologous subunits from rose, carrot, hibiscus, and alga tubulins, with more antigenic differences among alpha-subunits than among beta-subunits. Comparative colchicine-binding assays showed that rose and hibiscus tubulins bound 33% and 65%, respectively, of the colchicine bound by carrot tubulin and that higher plant tubulins bound much less colchicine than bovine brain tubulin under identical conditions.
Department of Developmental and Cell Biology, University of California, Irvine, CA 92717.
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