Biosynthesis of alpha-fetoprotein in cultured hepatoma cells.
Pulse and pulse-chase experiments demonstrated that a heterogeneous polypeptide with an apparent Mr = 68,000 was the first intracellular anti-alpha-fetoprotein (AFP)-precipitable polypeptide synthesized by rat Mc-A-RH-7777 hepatoma cells. The 68,000-dalton polypeptide may consist of polypeptides with apparent molecular weights ranging from 68,000 to 70,000. It was the precursor of two intracellular anti-AFP-precipitable polypeptides of 69,000 and 73,000 apparent molecular weight. The latter were secreted into the medium without further processing. The anti-AFP-precipitable polypeptides in both cells and medium incorporated [3H]glucosamine, indicating that these polypeptides are at least partially glycosylated. The 68,000-dalton polypeptide in cells was bound mostly to concanavalin A-Sepharose, whereas the 69,000-dalton polypeptide was entirely unbound. The 73,000-dalton polypeptide consisted of concanavalin A-bound and -unbound variants. Tunicamycin completely abolished the uptake of [3H]glucosamine into anti-AFT-precipitable polypeptides in both cells and medium, and the resulting polypeptide of apparent Mr = 66,000 did not bind to concanavalin A-Sepharose. Tunicamycin did not affect the synthesis or secretion of AFP by hepatoma cells.
D000818:Animals; D002460:Cell Line; D005944:Glucosamine / Q000378:metabolism; D007700:Kinetics; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D008970:Molecular Weight; D051381:Rats; D013462:Sulfur Radioisotopes; D014316:Tritium; D014415:Tunicamycin / Q000494:pharmacology; D000509:alpha-Fetoproteins / Q000096:biosynthesis*
D013462:Sulfur Radioisotopes; D000509:alpha-Fetoproteins; D014316:Tritium; D014415:Tunicamycin; D008715:Methionine; D005944:Glucosamine