Proline-rich (PxxP) motifs in HIV-1 Nef bind to SH3 domains of a subset of Src kinases and are required for the enhanced growth of Nef+ viruses but not for down-regulation of CD4.
Human immunodeficiency virus (HIV) and simian immunodeficiency virus Nef proteins contain a conserved motif with the minimal consensus (PxxP) site for Src homology region 3 (SH3)-mediated protein-protein interactions. Nef PxxP motifs show specific binding to biotinylated SH3 domains of Hck and Lyn, but not to those of other tested Src family kinases or less related proteins. A unique cooperative role of a distant proline is also observed. Endogenous Hck of monocytic U937 cells can be specifically precipitated by matrix-bound HIV-1 Nef, but not by mutant protein lacking PxxP. Intact Nef PxxP motifs are dispensable for Nef-induced CD4 down-regulation, but are required for the higher in vitro replicative potential of Nef+ viruses. Thus, CD4 down-regulation and promotion of viral growth are two distinct functions of Nef, and the latter is mediated via SH3 binding.
Rockefeller University, New York, NY 10021.
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D000595:Amino Acid Sequence; D015704:CD4 Antigens / Q000235:genetics; D015536:Down-Regulation; D015693:Gene Products, nef / Q000235:genetics / Q000378:metabolism*; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000235:genetics; D015497:HIV-1 / Q000235:genetics / Q000254:growth & development* / Q000276:immunology; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000821:virology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011392:Proline / Q000378:metabolism; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000145:classification / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051572:Proto-Oncogene Proteins c-hck; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D054311:nef Gene Products, Human Immunodeficiency Virus; D019061:src-Family Kinases
D015704:CD4 Antigens; D015693:Gene Products, nef; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D054311:nef Gene Products, Human Immunodeficiency Virus; D011392:Proline; D005982:Glutathione Transferase; D011505:Protein-Tyrosine Kinases; C496631:HCK protein, human; D051572:Proto-Oncogene Proteins c-hck; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases