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.
Department of Medicine, Howard Hughes Medical Institute, University of California, San Diego, School of Medicine, La Jolla 92093.
G M
GM
Walton
W S
WS
Chen
M G
MG
Rosenfeld
G N
GN
Gill
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