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Journal of Virology, March 1999, p. 1902-1908, Vol. 73, No. 3
Cell Biology Program, Memorial
Sloan-Kettering Cancer Center, New York, New York 10021
Received 31 July 1998/Accepted 24 November 1998
The human immunodeficiency virus type 1 (HIV-1)
Pr55gag gene product directs the assembly of
virions at the inner surface of the cell plasma membrane. The
specificity of plasma membrane binding by
Pr55gag is conferred by a combination of an
N-terminal myristoyl moiety and a basic residue-rich domain. Although
the myristate plus basic domain is also present in the p17MA
proteolytic product formed upon Pr55gag
maturation, the ability of p17MA to bind to membranes is significantly reduced. It was previously reported that the reduced membrane binding
of p17MA was due to sequestration of the myristate moiety by a
myristoyl switch (W. Zhou and M. D. Resh, J. Virol.
70:8540-8548, 1996). Here we demonstrate directly that treatment of
membrane-bound Pr55gag in situ with HIV-1
protease generates p17MA, which is then released from the membrane.
Pr55gag was synthesized in reticulocyte
lysates, bound to membranes, and incubated with purified HIV-1
protease. The p17MA product in the membrane-bound and soluble fractions
was analyzed following proteolysis. Newly generated p17MA initially was
membrane bound but then displayed a slow, time-dependent dissociation
resulting in 65% solubilization. Residual p17MA could be extracted
from the membranes with either high pH or high salt. Treatment of
membranes from transfected COS-1 cells with protease revealed that
Pr55gag was present within sealed membrane
vesicles and that the release of p17MA occurred only when detergent and
salt were added. We present a model proposing that the HIV-1 protease
is the "trigger" for a myristoyl switch mechanism that modulates
the membrane associations of Pr55gag and p17MA
in virions and membranes.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Human Immunodeficiency Virus Type 1 Protease
Triggers a Myristoyl Switch That Modulates Membrane Binding of
Pr55gag and p17MA
*
Corresponding author. Mailing address: Cell Biology
Program, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., Box
143, New York, NY 10021. Phone: (212) 639-2514. Fax: (212) 717-3317. E-mail: m-resh{at}ski.mskcc.org.
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