The effects on tubulin polymerization and associated guanosine triphosphate hydrolysis of aluminum ion, fluoride and fluoroaluminate species

The effects of aluminum ion, fluoride, and fluoroaluminate species on the assembly of tubulin in the presence of guanine nucleotides and the consequences of these ions on the associated GTPase of microtubules was investigated. Combinations of GDP and fluoroaluminate species were incapable of activating tubulin for polymerization, in contrast to other guanine nucleotide binding proteins, in which these species produce a functional GTP equivalent. Fluoride alone has an effect on GTP-magnesium-promoted microtubule assembly, causing an increased amount of polymer formation and a reduced rate of associated GTP hydrolysis. It is concluded that aluminum ion and fluoroaluminate species possess distinct mechanisms in inhibiting GTP hydrolysis of GTP-binding proteins and that subpopulations of GTP-binding proteins must exist based on differential sensitivities to these ions.