Analysis of deletions of the carboxyl terminus of the epidermal growth factor receptor reveals self-phosphorylation at tyrosine 992 and enhanced in vivo tyrosine phosphorylation of cell substrates.
The human epidermal growth factor receptor (EGFR) contains a large C' terminus distal to the protein tyrosine kinase domain that is conserved among members of its extended gene family. To investigate the C' terminus, a series of mutant EGFR cDNAs encoding progressive C'-terminal deletions were prepared and expressed in null recipient B82L cells. In vivo self-phosphorylation was retained in receptors truncated to residues 1052 and 1022 which lack the three identified sites of tyrosine self-phosphorylation. Receptors truncated to residue 991 did not undergo in vivo self-phosphorylation. Purified 1022 truncated receptor was self-phosphorylated to the extent of 1 mol of phosphate/mol of receptor protein. The deduced additional site of tyrosine self-phosphorylation at residue 992 was confirmed by tryptic phosphopeptide mapping and protein sequencing. EGFRs deleted to give C'-terminal residues 1052, 1022, 991, and 973 exhibited enhanced EGF-stimulated tyrosine phosphorylation of cell substrates in vivo, whereas deletion at residue 944 abolished all detectable EGF-stimulated protein tyrosine phosphorylation. These results indicate that ligand-induced self-phosphorylation is limited to the C' terminus of the EGFR and suggest that this region of the holoreceptor has an inhibitory function.
Walton
G M
GM
Department of Medicine, Howard Hughes Medical Institute, University of California, San Diego, School of Medicine, La Jolla 92093.
Chen
W S
WS
Rosenfeld
M G
MG
Gill
G N
GN
D004252:DNA Mutational Analysis; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008970:Molecular Weight; D010449:Peptide Mapping; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D010750:Phosphoproteins; D019000:Phosphotyrosine; D014443:Tyrosine; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases