Fig. 4. The tubulin polyglutamylase preparation displays ß-casein phosphorylation activity. 10 µl aliquots of successive fractions from the final hydroxyapatite chromatography were assayed for tubulin polyglutamylation activity while 5 µl aliquots were used in kinase assays with ß-casein as substrate. The kinase reactions were run on an SDS-gel and analysed by autoradiography. Note that the ß-casein phosphorylation activity exactly coelutes from the CHT-2 column with the tubulin glutamylation activity.