PREPARATION AND PROPERTIES OF AN ALKYLATED BRAIN PROTEIN RELATED TO STRUCTURAL SUBUNIT OF MICROTUBULES

The procedure for preparing a stable, purified protein from calf brain is described. The protein has the physical and chemical characteristics of the colchicine-binding protein of mammalian brain, which is presumably a component of the neural microtubules. The presence of a reducing agent during the preparative procedure and the alkylation of the sulfhydryl groups just prior to isolation of the purified protein circumvent the problem of aggregation which had complicated previous isolation procedures. The material is a glycoprotein of 70,000 mol wt which does not appear to contain any significant amount of α-helix or β-conformation. Depolarization of fluorescence studies show that it is a highly stable, compact molecule with a rotational relaxation time of 240 nsec at 5 °. © 1969.