Sequences in Rotavirus Glycoprotein VP7 That Mediate Delayed Translocation and Retention of the Protein in The Endoplasmic Reticulum

• Published in: The Journal of cell biology Vol. 111; no. 4; pp. 1343 - 1350
• Main Authors: Stirzaker, S. Clare, Poncet, Didier, Both, Gerald W.
• Format: Journal Article
• Language: English
• Published: New York, NY Rockefeller University Press 01-10-1990; The Rockefeller University Press
• Subjects: Amino Acid Sequence; Animals; Antigens, Viral - chemistry; Barns; Biological and medical sciences; Biological Transport - physiology; Capsid - chemistry; Capsid - metabolism; Capsid Proteins; Cell physiology; COS cells; DNA; Endoplasmic reticulum; Endoplasmic Reticulum - metabolism; Fundamental and applied biological sciences. Psychology; Glycoproteins; Glycosylation; Hybridity; Kinetics; Life Sciences; Membrane and intracellular transports; Microsomes; Molecular and cellular biology; Molecular Sequence Data; Protein Sorting Signals - physiology; Protein transport; Rotavirus; Rotavirus - physiology; Transfection; Ungulates; Leader peptide; Gel electrophoresis; Glycoproteins; Glycosylation; Microsome; Membrane translocation; Reoviridae; Simian rotavirus; Virus; Cell line; Bovine rotavirus; Transfection; Kinetics; Duovirus; Endoplasmic reticulum; Pulse labelling; GLYCOSILATION
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.111.4.1343

Glycosylation and translocation of the simian rotavirus protein VP7, a resident ER protein, does not occur co-translationally in vivo. In pulse-chase experiments in COS cells, nonglycosylated VP7 was still detectable after a 25-min chase period, although the single glycosylation site was only 18 residues beyond the signal peptide cleavage site. After labeling, glycosylated and nonglycosylated VP7 was recovered in microsomes but the latter was sensitive to trypsin (i.e., the nascent protein became membrane associated) but most of it entered the ER posttranslationally because of a rate-limiting step early in translocation. In contrast with the simian protein, bovine VP7 was glycosylated and translocated rapidly. Thus, delayed translocation per se was not required for retention of VP7 in the ER. By constructing hybrid proteins, it was further shown that the signal peptide together with residues 64-111 of the simian protein caused delayed translocation. The same sequences were also necessary and sufficient for retention of simian VP7 in the ER. The data are consistent with the idea that certain proteins are inserted into the ER membrane in a loop configuration.