Identification of tyrosine 67 in bovine brain myelin basic protein as a specific phosphorylation site for thymus p56lck.
The protein-tyrosine kinase p56lck exhibits a restricted substrate specificity in vitro but can efficiently phosphorylate bovine myelin basic protein (MBP). Results obtained from both peptide mapping and fast atom bombardment mass spectrometry indicate that tyrosine 67 in the sequence -Thr-Thr-His-Tyr67-Gly-Ser-Leu-Pro-Gln-Lys- in bovine MBP is the specific phosphorylation site. p56lck does not phosphorylate the acidic, cytoplasmic domain of erythrocyte band 3. In contrast, p40, another protein-tyrosine kinase purified from bovine thymus that readily phosphorylates band 3, does not phosphorylate MBP. Therefore, MBP and band 3 may prove to be useful substrates for distinguishing between various tyrosine kinases on the basis of substrate specificity. In addition, identification of the recognition sequence in MBP for p56lck may contribute to an understanding of the structural features of physiological substrates for this kinase.
Wang
Q
Q
Department of Medicinal Chemistry and Pharmacognosy, Purdue University, West Lafayette, Indiana 47907.
Smith
J B
JB
Harrison
M L
ML
Geahlen
R L
RL
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D008969:Molecular Sequence Data; D004676:Myelin Basic Protein / Q000378:metabolism*; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000302:isolation & purification; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000201:enzymology; D013950:Thymus Gland / Q000201:enzymology; D014443:Tyrosine
D004676:Myelin Basic Protein; D010748:Phosphopeptides; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)