In a previous communication we reported that the newly synthesized membrane glycoprotein of vesicular stomatitis virus could be transported in crude extracts of CHO cells from endoplasmic reticulum-derived membranes to membranes of the Golgi complex. This conclusion was an indirect one, based on the terminal glycosylation of this glycoprotein, a reaction that was dependent upon a Golgi-specific enzyme, UDP-GlcNAc transferase I. We show here that the Golgi fraction of rat liver will substitute for members of CHO cells as a source of transferase I in this reaction. The use of highly purified fractions of liver Golgi membranes, coupled with the ability to recover these membranes from incubations, has now permitted a direct demonstration of net transport of G protein to these heterologous Golgi membranes. This transport reaction is specific, in that the smooth endoplasmic reticulum fraction will not substitute for the Golgi fraction, is quantitatively significant, involving at least 30% of the viral glycoprotein, and is sustained only in the presence of both ATP and a soluble, cytosol fraction of liver cells.

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