Cdc2-mediated modulation of pp60c-src activity.
Following complete dephosphorylation, purified p60c-src was rephosphorylated with Csk. The Csk-phosphorylated form was isolated and found to be essentially inactive. Both the dephosphorylated p60c-src (Src A) and the inactive, phosphorylated pp60c-src (Src B) were then used to explore the regulatory role of other kinases and phosphatases. Phosphorylation by Cdc2 partially reactivated Csk-inactivated pp60c-src. This reactivation occurred in the absence of Tyr-527 dephosphorylation. Moreover, phosphorylation of Csk-treated pp60c-src by Cdc2 also facilitated complete reactivation by the protein-tyrosine phosphatase CD45 or by a synthetic phosphopeptide corresponding to the C-terminal, regulatory phosphorylation site (Tyr-527). These data indicate that the Src homology 2 domain of Csk-phosphorylated pp60c-src was more accessible for intermolecular interactions and that Tyr-527 was more readily dephosphorylated after treatment with Cdc2. In conjunction with in vivo studies, these data suggest that Cdc2 is involved in the regulation of pp60c-src during mitosis.
Stover
D R
DR
Research Department, Ciba-Geigy Ltd., Basel, Switzerland.
Liebetanz
J
J
Lydon
N B
NB
D000595:Amino Acid Sequence; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D000081247:CSK Tyrosine-Protein Kinase; D002474:Cell-Free System; D004305:Dose-Response Relationship, Drug; D017493:Leukocyte Common Antigens / Q000378:metabolism; D008969:Molecular Sequence Data; D015688:Oncogene Protein pp60(v-src) / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology; D010748:Phosphopeptides / Q000494:pharmacology; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D019061:src-Family Kinases
D010446:Peptide Fragments; D010748:Phosphopeptides; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D015688:Oncogene Protein pp60(v-src); D019061:src-Family Kinases; D016203:CDC2 Protein Kinase; D017493:Leukocyte Common Antigens; D017027:Protein Tyrosine Phosphatases