Cell-free synthesis and glycosylation of the major human-red-cell sialoglycoprotein, glycophorin A.
The human erythroid cell line, K562, synthesizes the major red cell sialoglycoprotein, glycophorin A. We have isolated an mRNA fraction which codes for glycophorin A from K562 cells and studied the synthesis of the sialoglycoprotein in a rabbit reticulocyte cell-free system. In the absence of membranes a precursor form of glycophorin A was synthesized. This was identified using specific anti-(glycophorin A) serum. The apparent molecular weight of the carbohydrate-free precursor of glycophorin A was 19 500. This exceeds the molecular weight of the glycophorin A apoprotein by approximately 5000. In the presence of membranes from dog pancreas, the synthesized glycophorin A precursor was N-glycosylated and probably also O-glycosylated. The oligosaccharide chains remained incomplete and the glycoprotein synthesized in vitro corresponded to the glycosylated precursor of glycophorin A obtained in intact cells.
D000818:Animals; D002460:Cell Line; D002474:Cell-Free System; D004912:Erythrocytes; D006021:Glycophorins / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D012795:Sialoglycoproteins / Q000235:genetics*
D006021:Glycophorins; D012333:RNA, Messenger; D012795:Sialoglycoproteins