The synthesis of complex-type oligosaccharides. II. Characterization of the processing intermediates in the synthesis of the complex oligosaccharide units of the vesicular stomatitis virus G protein

G1 and G2 are two forms of the membrane-integrated G protein of vesicular stomatitis virus that migrate differently in gel electrophoresis because G1 is modified by high-mannose and G2 by complex-type oligosaccharide side chains. The cytoplasmic domain in G1 is less exposed to cleavage by several proteases than in G2 molecules. Acylation by palmitic acid as well as inhibition of carbohydrate processing by swainsonine and deoxynojirimycin resulted in the same pattern of proteolytic sensitivity of both glycoproteins as in untreated cells. In contrast, accessibility of the cytoplasmic domain to proteases did not change when the intracellular transport of the G protein was blocked in carbonyl cyanide m-chlorophenylhydrazone- or monensin-treated BHK-21 cells, respectively. The results suggest that the increase in accessibility of the cytoplasmic tail of the G protein occurs after the monensin block in the trans-Golgi and might reflect a conformational change of functional significance--i.e., making the cytoplasmic domain of the viral spike protein competent for its interaction with the viral core, inducing thereby the formation of the budding virus particle.

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Processing of the asparagine-linked oligosaccharides of secreted and intracellular forms of the vesicular stomatitis virus G protein: in vivo evidence of Golgi apparatus compartmentalization.

The Journal of Cell Biology ◽

10.1083/jcb.101.2.460 ◽

1985 ◽

Vol 101 (2) ◽

pp. 460-469 ◽

Cited By ~ 24

Author(s):

C A Gabel ◽

J E Bergmann

Keyword(s):

Sialic Acid ◽

Golgi Apparatus ◽

G Protein ◽

Vesicular Stomatitis Virus ◽

Vesicular Stomatitis Virus Glycoprotein ◽

Complex Type ◽

Major Class ◽

Vesicular Stomatitis ◽

High Mannose

The structures of the asparagine-linked oligosaccharides of several variant forms of the vesicular stomatitis virus glycoprotein transiently expressed from cloned cDNAs have been determined. Glycopeptides isolated from forms of the G protein that reach the cell surface or that are secreted into the medium are virtually identical; they contain complex-type oligosaccharides whose nonreducing ends terminate in galactose and sialic acid residues. In contrast, forms of the G protein that remain intracellular possess oligosaccharides at intermediate stages in the processing pathway. One deletion mutant, delta 1473, codes for a protein that remains in the rough endoplasmic reticulum (Rose, J. K., and J. E. Bergmann, 1982, Cell, 30:753-762) and contains only high mannose-type oligosaccharides. Another mutant, delta 1554, codes for a glycoprotein that contains oligosaccharides of primarily two classes. One class is of the high mannose type and is similar to those found on the protein coded for by delta 1473. However, the major class contains biantennary and more highly branched complex-type oligosaccharides that terminate in N-acetylglucosamine rather than galactose or sialic acid residues. These data suggest that the protein coded for by delta 1554 migrates to the Golgi apparatus, but does not enter the more distal compartment(s) of the organelle which contains galactosyl- and sialyltransferases.

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