Tubulins from different higher plant species are immunologically nonidentical and bind colchicine differentially

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Abstract
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 α- and β-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 β-subunits than among the α-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 α-subunits than among β-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.