EFFECTS OF ANTI-MICROTUBULE DRUGS ON INVITRO POLYMERIZATION OF TUBULIN FROM MUNG BEAN

Effects of anti-microtubule drugs on tubulin polymerization in vitro were investigated using purified mung bean (Vigna radiata) tubulin. Colchicine induced the formation of macrotubules at the relatively low concentration of 10-mu-M and the appearance of corkscrew-like filaments from the ends of the macrotubules at concentrations of more than 100-mu-M. Vinblastine substantially inhibited polymerization at 1-mu-M and caused the formation of paracrystals at concentrations greater than 10-mu-M. Oryzalin inhibited polymerization at 1-mu-M partially and at 10-mu-M completely. Paracrystal formation was also induced by cremart at 10-mu-M, but these paracrystals appeared to be more rigid than those induced by vinblastine. Amiprophos methyl (APM), with a chemical configuration similar to cremart, substantially inhibited polymerization at 1-mu-M, but the formation of paracrystals was weak. Griseofulvin at 10-mu-M also inhibited the polymerization of tubulin while at higher concentrations aggregates of helices were formed. Inhibition of polymerization by phenylcarbamate herbicides was more effective than that caused by benzimidazoylcarbamate fungicides. The effects of drugs on in vitro preformed (MTs) were also investigated. Colchicine and vinblastine showed identical effects to those on the polymerization process. Griseofulvin, cremart and APM induced only macrotubule formation while the other drugs tested had no major effects.