Purification and characterization of a pp60c-src-related tyrosine kinase that effectively phosphorylates a synthetic peptide derived from p34cdc2.
A protein tyrosine kinase has been purified from the particulate fraction of bovine spleen to a specific activity of 0.217 mumol/min/mg at 100 microM ATP and 3 mM [Val5] angiotensin II. Both the angiotensin phosphorylation activity and immunoreactivity towards an antibody preparation raised against a synthetic peptide containing the autophosphorylation site of pp60c-src, Cys-src(403-421), were monitored during the purification. The purified sample displayed three closely spaced protein bands with molecular weights of 50-55 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. All bands could be phosphorylated exclusively on tyrosine residues under autophosphorylation conditions. All reacted on immunoblots with an antibody raised against a synthetic peptide corresponding to the consensus autophosphorylation site of members of the pp60c-src family of tyrosine kinases. Tryptic phosphopeptide maps of the three proteins were essentially indistinguishable. The results suggest that the purified enzyme preparation contained mainly three closely related pp60c-src-family protein tyrosine kinases or a pp60src-family protein tyrosine kinase modified posttranslationally to give three closely spaced protein bands on sodium dodecyl sulfate gel. Neither of these proteins appears to be pp60c-src or p56lck. The spleen protein tyrosine kinase was found to phosphorylate a p34cdc2 kinase peptide, Cys-cdc2(8-20), which contained the regulatory tyrosine residue Tyr-15 about 20 times better than [Val5]angiotensin II or Cys-src(403-421) peptide at a peptide substrate concentration of 1 mM. In contrast, epidermal growth factor receptor kinase partially purified from A431 cells did not show preference for Cys-cdc2(8-20) as its substrate. Although Cys-cdc2(8-20) contained two tyrosine residues, only the tyrosine corresponding to Tyr-15 in p34cdc2 was phosphorylated by the spleen tyrosine kinase. The observation suggests that the primary structure surrounding Tyr-15 of p34cdc2 contains substrate structural determinants specific for the spleen tyrosine kinase.
Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, Alberta, Canada.
C M
CM
Litwin
H C
HC
Cheng
J H
JH
Wang
D000595:Amino Acid Sequence; D000818:Animals; D000918:Antibody Specificity; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002417:Cattle; D002850:Chromatography, Gel; D004797:Enzyme-Linked Immunosorbent Assay; D015151:Immunoblotting; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010449:Peptide Mapping; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000276:immunology / Q000378:metabolism*; D013154:Spleen / Q000201:enzymology*; D013379:Substrate Specificity
D011505:Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); D016203:CDC2 Protein Kinase