Journal of Virology, November 2001, p. 10537-10542, Vol. 75, No. 21
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.21.10537-10542.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Departments of Microbiology1 and Medicine,4 University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6148, and Department of Biochemistry2 and Center for Biomolecular Interaction Analysis,3 University of Utah School of Medicine, Salt Lake City, Utah 84132
Received 13 June 2001/Accepted 2 August 2001
The nonstructural human immunodeficiency virus type 1 Vpr protein is packaged into progeny virions at significant levels (~200 copies/virion). Genetic analyses have demonstrated that efficient Vpr packaging is dependent upon a leucine-X-X-leucine-phenylalanine (LXXLF) motif located in the p6Gag domain of the structural Gag polyprotein. Recombinant proteins spanning full-length Vpr (Vpr1-97) or the amino-terminal 71 amino acids (Vpr1-71) formed specific complexes with recombinant p6 proteins in vitro. Complex formation required an intact LXXLF motif and exhibited an intrinsic dissociation constant of ~75 µM. Gel filtration and cross-linking analyses further revealed that Vpr1-71 self-associated in solution. Our experiments demonstrate that Vpr can bind directly and specifically to p6 and suggest that oligomerization of both Vpr and Gag may serve to increase the avidity and longevity of Vpr-Gag complexes, thereby ensuring efficient Vpr packaging.
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