Glycosylation in vitro of Semliki‐Forest‐Virus and Influenza‐Virus Glycoproteins and Its Suppression by Nucleotide‐2‐deoxy‐hexose

Abstract

Cell-free enzyme preparations from cultured fibroblasts infected with Semliki forest virus or fowl plague virus (an influenza A virus) incorporate [¹⁴C]mannose from GDP-[¹⁴C]mannose into dolichol-phosphate-mannose, lipid-linked oligosaccharides and into endogenous virus-specific glycoproteins. When GDP-2-deoxy-d-[¹⁴C]glucose serves as substrate 2-deoxy-d-[¹⁴C]glucose is transferred to dolichol phosphate yielding dolichol-monophosphate-2-deoxy-d-[¹⁴C]glucose. UDP-2-deoxy-d-[¹⁴C]-glucose gives rise also to a lipid which, however, is not a polyprenol derivative. The transfer of [¹⁴C]mannose to lipid-extractable fractions and glycoproteins in vitro is blocked by GDP-2-deoxy-d-glucose. It can be restored by exogenous dolichol monophosphate only with regard to the formation of dolichol-monophosphate-[¹⁴C]mannose. GDP-2-deoxy-d-glucose, however, does not inhibit the transfer of [¹⁴C]mannose-labelled oligosaccharides into glycoproteins. UDP-2-deoxy-d-glucose has no inhibitory effect on transfer reactions of [¹⁴C]mannose from GDP-[¹⁴C]mannose into various lipid fractions or into glycoprotein. It is concluded therefore, that the inhibition of glycosylation brought about by 2-deoxyglucose in vivo is caused by an interference of its GDP derivative with the formation of a correct lipid-oligosaccharide.