Transient activity of Golgi-like membranes as donors of vesicular stomatitis viral glycoprotein in vitro.

Abstract

Previous reports demonstrated that the vesicular stomatitis viral glycoprotein (G protein), initially present in membranes of a Chinese hamster ovary (CHO) mutant cell line (clone 15B) incapable of terminal glycosylation, can be transferred in vitro to exogenous Golgi membranes and glycosylated there. Presently evidence is presented that Golgi-like membranes serve as donors of G protein in this process. Pulse-chase experiments revealed that the donor activity of membranes is greatest at .apprx. 10 min of chase, when G protein arrived at the Golgi stacks. Additional evidence that the G protein transferred to exogenous Golgi membranes in vitro had already entered the Golgi membranes in vivo was provided by observations that its oligosaccharides had already been trimmed, and that its distribution in a sucrose density gradient was coincident with that of enzymatic markers of Golgi membranes. The capacity of this Golgi-like membrane to serve as donor is transient, declining within 5 min after trimming in vivo as the G protein enters a nontransferable pool. The rapidity of the process suggests that both the transferable and nontransferable pools of G protein reside in Golgi-like membranes.