Characteristics of tubulin aggregation by tubulin-binding proteins from brain and by synthetic polycations

A basic fraction from brain cytosol was found to contain two or more tubulin-binding proteins, able to induce aggregation of tubulin accompanied by hydrolysis of GTP. In some respects tubulin aggregation by the brain proteins was similar to its aggregation by polylysine. The burst of GTP hydrolysis accompanying tubulin aggregation by polylysine had the following characteristics: enhanced by salt and abolished by low temperature; not stoichiometric with the amount of tubulin precipitated and actually maximal at relatively low polylysine concentration; uncoupled temporally from aggregation, which occurred over a much shorter interval.