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J. Virol., 10 1995, 6473-6478, Vol 69, No. 10
ML Clarke, LJ Lockett and GW Both
The sequences responsible for binding rotavirus glycoprotein VP7 to the
membrane of the endoplasmic reticulum (ER) have not been identified. Here
we show that the sequences which promote membrane binding in vitro are
distinct from the N-terminal sequences which promote retention of VP7 in
the ER in vivo. The role of the C-terminal region in membrane binding was
also examined by using truncation mutants. Membrane binding in vitro was
reduced but not abolished by removing up to 102 residues from the C
terminus. The data suggest that the last 36 residues of VP7 may be present
in the membrane or translocation pore, possibly with the C terminus
protruding into the cytoplasm, since these residues contribute to, but do
not account for, membrane binding. Surprisingly, modified forms of VP7
which are secreted from transfected cells showed the same membrane-binding
properties in vitro as the protein retained in the ER membrane. Thus,
secreted VP7 may not be present as a soluble polypeptide in the ER. A model
to explain these results is presented. Previously published data are
consistent with the idea that the highly conserved C terminus of nascent
VP7 could have a cytoplasmic orientation which is important for assembly of
mature virus particles.
Copyright © 1995, American Society for Microbiology
Membrane binding and endoplasmic reticulum retention sequences of rotavirus VP7 are distinct: role of carboxy-terminal and other residues in membrane binding
Division of Biomolecular Engineering, Commonwealth Scientific and Industrial Research Organisation, North Ryde, New South Wales, Australia.
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