Differences in protein phosphorylation in vivo and in vitro between wild type and dunce mutant strains of Drosophila melanogaster

1. 1. The protein phosphorylation patterns of wild type and dunce mutant strains of Drosophila melanogaster, as detected by sodium dodecylsulfate-gel electrophoresis and autoradiography, have been compared. 2. 2. After labelling in vivo with 32P i or in vitro in homogenates with [γ- 32P]ATP, radioactive bands at and above apparent polypeptide mol. wt ~ 110,000 were more pronounced in dunce fly heads than in wild type heads. 3. 3. When labelling in vitro, in dunce M11 there appeared a radioactive band at apparent mol. wt ≈ 53,000 that was faintly visible in the wild strain. 4. 4. The same band could be intensified in both strains by adding cyclic AMP to the homogenate or by performing homogenization in the presence of theophylline. 5. 5. The data suggest that the mol. wt % 53,000 protein is a substrate for cyclic AMP-dependent protein kinase.