Evidence for the participation of saccharide-lipids in the synthesis of the oligosaccharide chain of ovalbumin.

摘要: To obtain information on the mechanism of glycosylation ovalbumin, three types experiments were performed with either hen oviduct membrane preparations or tissue slices and antibiotic tunicamycin. First, involving addition tunicamycin to membranes demonstrated that this inhibited synthesis a N-acetylglucosaminyl-lipid properties N-acetyl-glucosaminylpyrophosphorylpolyisoprenol. No inhibitory effects other steps in oligosaccharide-lipid observed. Thus, inhibits lipid-linked pathway for protein by blocking first step oligosaccharide-lipid, namely, N-acetylglucosaminylpyrophosphorylpolyisoprenol. Second, using prepared from preincubated tunicamycin, it was found mannosylphosphoryldolichol only saccharide-lipid synthesized. This result indicates administered vivo depletes endogenous pools N-acetylglucosamine-lipid precursors manner consistent its activity vitro. Finally, incubated presence synthesized polypeptide chain ovalbumin at almost normal rates. However, newly did not contain labeled N-acetylglucosamine mannose had unglycosylated ovalbumin. These results indicate saccharide-lipids participate assembly core oligosaccharide secretory glycoprotein,