Widespread Occurrence of Ganglioside-Stimulated Protein Kinase in Animal Brains

Abstract

Ganglioside-stimulated protein kinase, designated PKJ, had been found in several animal brains. These include guinea pig, rabbit, rat, and duck brains. All of the four brain PKJ could be extracted from the particulate fractions using nonionic detergent nonidet P-40 and purified by using identical DEAE-cellu-lose and phenyl-Sepharose chromatographic methods. These results suggest that PKJ from different animal brains has similar ionic and hydrophobic characteristics. All four of the partially purified PKJ preparations could undergo autophosphorylations in the presence of trisialoganglioside G_T1b and ³²P-ATP. Analyses of the autophosphorylated proteins by using SDS-polyacrylamide gel electrophoresis and subsequent autoradiography revealed one major radioactive band with apparent M_r = 68,000. The range of ganglioside-stimulated auto-phosphorylation was between 6- and 10-fold. The structural similarities of the different animal brain PKJ were further determined by using one-dimensional peptide mapping techniques. Limited proteolytic cleavages of the ³²P-labeled 68-kD bands with staphylococcal aureus V-8 protease resulted in four major radioactive fragments with apparent M_r corresponding to 22, 20, 18 and 15-kD, respectively. By contrast, digestion with chymotrypsin revealed only two major radioactive bands with apparent M_r of 43 and 26 kD, respectively. These findings indicate that PKJ from guinea pig, rabbit, rat, and duck brains may have similar primary structures.