Studies on the phosphorylation of myelin basic protein by protein kinase C and adenosine 3':5'-monophosphate-dependent protein kinase.
The substrate specificity of protein kinase C was studied and compared with that of cyclic AMP-dependent protein kinase (protein kinase A) by using bovine brain myelin basic protein as a model substrate. This basic protein was phosphorylated at multiple sites by both of these protein kinases. In this analysis, the basic protein was thoroughly phosphorylated in vitro with [gamma-32P]ATP and each protein kinase, and then digested with trypsin. The resulting radioactive phosphopeptides were isolated by gel filtration followed by high performance liquid chromatography on a reverse-phase column. Subsequent amino acid analysis and/or sequential Edman degradation of the purified phosphopeptides, together with the known primary sequence of this protein, revealed that Ser-46 and Ser-151 were specifically phosphorylated by protein kinase C, whereas Thr-34 and Ser-115 were phosphorylated preferentially by protein kinase A. Both kinases reacted with Ser-8, Ser-11, Ser-55, Ser-110, Ser-132, and Ser-161 at various reaction velocities. Contrary to protein kinase A, protein kinase C appears to react preferentially with seryl residues that are located at the amino-terminal side close to lysine or arginine. The seryl residues that are phosphorylated commonly by these two protein kinases have basic amino acids at both the amino- and carboxyl-terminal sides. These results provide some clues to understanding the rationale that these kinases may show different but sometimes similar functions depending on the structure of target phosphate acceptor proteins.
A
A
Kishimoto
K
K
Nishiyama
H
H
Nakanishi
Y
Y
Uratsuji
H
H
Nomura
Y
Y
Takeyama
Y
Y
Nishizuka
D000595:Amino Acid Sequence; D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology*; D007700:Kinetics; D004676:Myelin Basic Protein / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D013379:Substrate Specificity; D014357:Trypsin / Q000378:metabolism
D004676:Myelin Basic Protein; D010455:Peptides; D010750:Phosphoproteins; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C; D014357:Trypsin