Zinc-induced self-assembly of goat brain tubulin: some novel aspects

Abstract

Unlike normal microtubule assembly, the in vitro assembly of DEAE-purified goat brain tubulin in presence of Zn(II) is not inhibited by suprastoichiometric concentrations of antimicrotubular drugs like colchicine and podophyllotoxin. However, assembly in the presence of Zn(II) is inhibited by vinblastine. Vinblastine sensitivity of the assembly process depends on the Mg(II) concentration in the assembly medium. Like normal microtubules, Zn(II)-induced polymers are sensitive to cold. The polymers assembled in presence of Zn(II) are readily disassembled on treatment with Zn(II)-chelators like EDTA or o-phenanthroline, indicating that the binding of Zn(II) to tubulin is essential for maintaining the polymeric structure. MAPs, Microtubule-associated proteins; MES, 2-(N-Morpholino) ethane sulfonic acid; MT, Microtubule; CD, Colchicine-tubulin dimer complex; GTP, Guanosine-5'-triphosphate; SDS, Sodium dodecyl sulphate; EDTA, Ethylenediamine-tetraacetic acid; Buffer A, 0.1 M MES (pH 6.4), 0.5 mM MgCl₂, 1 mM GTP; Buffer B, 4 M glycerol in buffer A.