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Journal of Virology, December 2001, p. 11544-11554, Vol. 75, No. 23
Department of Microbiology, University of
Alabama at Birmingham, Birmingham, Alabama 35294
Received 6 April 2001/Accepted 7 August 2001
The Rous sarcoma virus (RSV) transmembrane (TM) glycoprotein is
modified by the addition of palmitic acid. To identify whether conserved cysteines within the hydrophobic anchor region are the site(s) of palmitoylation, and to determine the role of acylation in
glycoprotein function, cysteines at residues 164 and 167 of the TM
protein were mutated to glycine (C164G, C167G, and C164G/C167G). In
CV-1 cells, palmitate was added to env gene products
containing single mutations but was absent in the double-mutant Env.
Although mutant Pr95 Env precursors were
synthesized with wild-type kinetics, the phenotypes of the mutants
differed markedly. Env-C164G had properties similar to those of the
wild type, while Env-C167G was degraded faster, and Env containing the
double mutant C164G/C167G was very rapidly degraded. Degradation
occurred after transient plasma membrane expression. The decrease in
steady-state surface expression and increased rate of internalization
into endosomes and lysosomes paralleled the decrease in
palmitoylation observed for the mutants. The phenotypes of mutant
viruses were assessed in avian cells in the context of the pATV8R
proviral genome. Virus containing the C164G mutation replicated with
wild-type kinetics but exhibited reduced peak reverse transcriptase
levels. In contrast, viruses containing either the C167G or the
C164G/C167G mutation were poorly infectious or noninfectious,
respectively. These phenotypes correlated with different degrees of
glycoprotein incorporation into virions. Infectious revertants of the
double mutant demonstrated the importance of cysteine-167 for efficient
plasma membrane expression and Env incorporation. The observation that
both cysteines within the membrane-spanning domain are accessible for
acylation has implications for the topology of this region, and a model
is proposed.
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.23.11544-11554.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Palmitoylation of the Rous Sarcoma Virus
Transmembrane Glycoprotein Is Required for Protein Stability and
Virus Infectivity

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Corresponding author. Mailing address: Department of
Microbiology, University of Alabama at Birmingham, 845 19th St. South, Birmingham, AL 35294. Phone: (205) 934-4321. Fax: (205) 924-1640. E-mail: ehunter{at}uab.edu
Present address: Viral Antigens Inc., Memphis, Tenn.
Present address: Laboratory of Molecular Biology, NIMH, Bethesda, Md.
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