A basic protein from bovine brain that co-precipitates with tubulin in vitro.

A 193 kDa protein consisting of 58 kDa subunits, which has pI values of 8.50 and 8.65, was purified from bovine brain cytosol. It formed heavy precipitates with tubulin, and the molar ratio of tubulin dimer to this protein in the precipitate was 3.2. In contrast to microtubules containing ordinary microtubule-associated proteins, these complexes remained stable against cold and 1 mM CaCl2.