title: Stoichiometry of the antiviral protein APOBEC3G in HIV-1 virions.
abstract: A host cytidine deaminase, APOBEC3G (A3G), inhibits replication of human immunodeficiency virus type 1 (HIV-1) by incorporating into virions in the absence of the virally encoded Vif protein (Deltavif virions), at least in part by causing G-to-A hypermutation. To gain insight into the antiretroviral function of A3G, we determined the quantities of A3G molecules that are incorporated in Deltavif virions. We combined three experimental approaches-reversed-phase high-pressure liquid chromatography (HPLC), scintillation proximity assay (SPA), and quantitative immunoblotting-to determine the molar ratio of A3G to HIV-1 capsid protein in Deltavif virions. Our studies revealed that the amount of the A3G incorporated into Deltavif virions was proportional to the level of its expression in the viral producing cells, and the ratio of the A3G to Gag in the Deltavif virions produced from activated human peripheral blood mononuclear cells (PBMC) was approximately 1:439. Based on previous estimates of the stoichiometry of HIV-1 Gag in virions (1400-5000), we conclude that approximately 7 (+/-4) molecules of A3G are incorporated into Deltavif virions produced from human PBMCs. These results indicate that virion incorporation of only a few molecules of A3G is sufficient to inhibit HIV-1 replication.
authors.affiliation: Viral Mutation Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute-Frederick, P. O. Box B, Bldg. 535, Rm. 334, Frederick, MD 21702, USA.
authors.forename: Hongzhan
authors.initials: H
authors.lastname: Xu
authors.forename: Elena
authors.initials: E
authors.lastname: Chertova
authors.forename: Jianbo
authors.initials: J
authors.lastname: Chen
authors.forename: David E
authors.initials: DE
authors.lastname: Ott
authors.forename: James D
authors.initials: JD
authors.lastname: Roser
authors.forename: Wei-Shau
authors.initials: WS
authors.lastname: Hu
authors.forename: Vinay K
authors.initials: VK
authors.lastname: Pathak
mesh_terms: D000071480:APOBEC-3G Deaminase; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D003564:Cytidine Deaminase; D017353:Gene Deletion; D015683:Gene Products, gag / Q000032:analysis; D016346:Gene Products, vif / Q000235:genetics; D015497:HIV-1 / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D006801:Humans; D015151:Immunoblotting; D007963:Leukocytes, Mononuclear / Q000201:enzymology / Q000378:metabolism; D009700:Nucleoside Deaminases / Q000032:analysis*; D012097:Repressor Proteins / Q000032:analysis*; D012588:Scintillation Counting; D014771:Virion / Q000737:chemistry*; D014779:Virus Replication; D054320:vif Gene Products, Human Immunodeficiency Virus
chemical_list: D015683:Gene Products, gag; D016346:Gene Products, vif; D012097:Repressor Proteins; D054320:vif Gene Products, Human Immunodeficiency Virus; D009700:Nucleoside Deaminases; D000071480:APOBEC-3G Deaminase; C464924:APOBEC3G protein, human; D003564:Cytidine Deaminase