Biosynthesis of the protein encoded by the c-met proto-oncogene.
The proto-oncogene c-met encodes a transmembrane protein with structural features of a growth factor receptor. We have previously shown that the c-met protein (c-Met) is a heterodimer of two disulphide linked chains of 50 kd (alpha) and 145 kd (beta). In this work we have studied the biosynthesis of the c-met product in a gastric carcinoma cell line (GTL-16) where the c-met gene is amplified and overexpressed. Following metabolic labelling of the cells in the presence of tunicamycin, anti-met antibodies immunoprecipitate a protein of 150 kd. In pulse-chase experiments carried out in the absence of tunicamycin, a 170 kd product appears first. Within the next few minutes, this precursor modifies its SDS migration, probably as a consequence of modification(s) of its intra-chain disulphide bonds. After 45 min of chase, this single polypeptide precursor is cleaved to form a 50 kd alpha subunit and a 145 kd beta subunit that are joined by disulphide bonds in an alpha beta complex with an apparent molecular weight of 190 kd. The presence of N-linked oligosaccharides in both the precursor and the mature protein was shown by enzymatic de-glycosylation of the immunoprecipitated proteins. The half-life of the mature protein was calculated to be approximately 5h. The c-met protein has similar structure and biosynthesis in other human cell lines.
Giordano
S
S
Department of Biomedical Sciences & Oncology, University of Torino, Italy.
Di Renzo
M F
MF
Narsimhan
R P
RP
Cooper
C S
CS
Rosa
C
C
Comoglio
P M
PM
D002460:Cell Line; D004220:Disulfides / Q000032:analysis; D005944:Glucosamine / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D008715:Methionine / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D019859:Proto-Oncogene Proteins c-met; D011519:Proto-Oncogenes; D013274:Stomach Neoplasms; D014415:Tunicamycin / Q000494:pharmacology
D004220:Disulfides; C000715470:MAS1 protein, human; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D014415:Tunicamycin; D008715:Methionine; D011505:Protein-Tyrosine Kinases; D019859:Proto-Oncogene Proteins c-met; D005944:Glucosamine