The epidermal growth factor receptor phosphorylates GTPase-activating protein (GAP) at Tyr-460, adjacent to the GAP SH2 domains.
GTPase-activating protein (GAP) stimulates the ability of p21ras to hydrolyze GTP to GDP. Since GAP is phosphorylated by a variety of activated or oncogenic protein-tyrosine kinases, it may couple tyrosine kinases to the Ras signaling pathway. The epidermal growth factor (EGF) receptor cytoplasmic domain phosphorylated human GAP in vitro within a single tryptic phosphopeptide. The same GAP peptide was also apparently phosphorylated on tyrosine in EGF-stimulated rat fibroblasts. Circumstantial evidence suggested that residue 460 might be the site of GAP tyrosine phosphorylation. This possibility was confirmed by phosphorylation of a synthetic peptide corresponding to the predicted tryptic peptide containing Tyr-460. Alteration of Tyr-460 to phenylalanine by site-directed mutagenesis diminished the in vitro phosphorylation of a bacterial GAP polypeptide by the EGF receptor. We conclude that Tyr-460 is a site of GAP tyrosine phosphorylation by the EGF receptor in vitro and likely in vivo. GAP Tyr-460 is located immediately C terminal to the second GAP SH2 domain, suggesting that its phosphorylation might have a role in regulating protein-protein interactions.
Liu
X Q
XQ
Division of Molecular and Developmental Biology, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada.
Pawson
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes; D010446:Peptide Fragments / Q000302:isolation & purification; D010449:Peptide Mapping; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection; D014357:Trypsin; D014443:Tyrosine; D020703:ras GTPase-Activating Proteins
D020690:GTPase-Activating Proteins; D015345:Oligonucleotide Probes; D010446:Peptide Fragments; D011506:Proteins; D011993:Recombinant Fusion Proteins; D020703:ras GTPase-Activating Proteins; D014443:Tyrosine; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D014357:Trypsin