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Virion infectivity factor



Human immunodeficiency virus 1
Unreviewed-Annotation score: Annotation score: 3 out of 5-Experimental evidence at transcript leveli


Counteracts the innate antiviral activity of host APOBEC3F and APOBEC3G. Forms a complex with host APOBEC3F and APOBEC3G thus preventing the entry of these lethally hypermutating enzymes into progeny virions. Recruits an active E3 ubiquitin ligase complex composed of elongin BC, CUL5, and RBX2 to induce polyubiquitination of APOBEC3G and APOBEC3F. In turn, they are directed to the 26S proteasome for degradation. Vif interaction with APOBEC3G also blocks its cytidine deaminase activity in a proteasome-independent manner, suggesting a dual inhibitory mechanism. May interact directly with APOBEC3G mRNA in order to inhibit its translation. Seems to play a role in viral morphology by affecting the stability of the viral nucleoprotein core. Finally, Vif also contributes to the G2 cell cycle arrest observed in HIV infected cells.UniRule annotation


HIV-1 lineages are divided in three main groups, M (for Major), O (for Outlier), and N (for New, or Non-M, Non-O). The vast majority of strains found worldwide belong to the group M. Group O seems to be endemic to and largely confined to Cameroon and neighboring countries in West Central Africa, where these viruses represent a small minority of HIV-1 strains. The group N is represented by a limited number of isolates from Cameroonian persons. The group M is further subdivided in 9 clades or subtypes (A to D, F to H, J and K).UniRule annotation
Required for replication in 'nonpermissive' cells, including primary T-cells, macrophages and certain T-cell lines, but is dispensable for replication in 'permissive' cell lines, such as 293T cells. In nonpermissive cells, Vif-defective viruses can produce virions, but they fail to complete reverse transcription and cannot successfully infect new cells.UniRule annotation
Vif-defective viruses show catastrophic failure in reverse transcription due to APOBEC-induced mutations that initiate a DNA base repair pathway and compromise the structural integrity of the ssDNA. In the absence of Vif, the virion is morphologically abnormal.UniRule annotation

GO - Molecular functioni

GO - Biological processi


Molecular functionRNA-bindingUniRule annotation
Biological processHost-virus interactionUniRule annotationSAAS annotation, Ubl conjugation pathwayUniRule annotationSAAS annotation

Names & Taxonomyi

Protein namesi
Recommended name:
Virion infectivity factorUniRule annotation
Short name:
VifUniRule annotation
Alternative name(s):
SOR proteinUniRule annotation
Cleaved into the following 2 chains:
p17UniRule annotation
p7UniRule annotation
Gene namesi
Name:vifUniRule annotationImported
OrganismiHuman immunodeficiency virus 1Imported
Taxonomic identifieri11676 [NCBI]
Taxonomic lineageiVirusesRetro-transcribing virusesRetroviridaeOrthoretrovirinaeLentivirusPrimate lentivirus group
Virus hostiHomo sapiens (Human) [TaxID: 9606]

Subcellular locationi

  • Host cell membrane UniRule annotationSAAS annotation; Peripheral membrane protein UniRule annotationSAAS annotation; Cytoplasmic side UniRule annotationSAAS annotation
  • Host cytoplasm UniRule annotation
  • Virion UniRule annotationSAAS annotation
  • Note: In the cytoplasm, seems to colocalize with intermediate filament vimentin. A fraction is associated with the cytoplasmic side of cellular membranes, presumably via the interaction with Pr55Gag precursor. Incorporated in virions at a ratio of approximately 7 to 20 molecules per virion.UniRule annotation

GO - Cellular componenti

Keywords - Cellular componenti

Host cell membraneUniRule annotationSAAS annotation, Host cytoplasmUniRule annotationSAAS annotation, Host membrane, Membrane, VirionUniRule annotationSAAS annotation

PTM / Processingi

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Modified residuei96Phosphothreonine; by host MAP4K1UniRule annotation1
Modified residuei144Phosphoserine; by hostUniRule annotation1
Modified residuei155Phosphothreonine; by hostUniRule annotation1
Modified residuei165Phosphoserine; by host MAP4K1UniRule annotation1
Modified residuei188Phosphothreonine; by hostUniRule annotation1

Post-translational modificationi

Highly phosphorylated on serine and threonine residues.UniRule annotation
Polyubiquitinated and degraded by the proteasome in the presence of APOBEC3G.UniRule annotation
Processed in virion by the viral protease.UniRule annotation


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sitei150 – 151Cleavage in virion (by viral protease)UniRule annotation2

Keywords - PTMi

PhosphoproteinUniRule annotation, Ubl conjugationUniRule annotation



Expressed late during infection in a Rev-dependent manner.UniRule annotation


Subunit structurei

Homomultimer; in vitro and presumably in vivo. Interacts with viral RNA and Pr55Gag precursor; these interactions mediate Vif incorporation into the virion. Interacts with the viral reverse transcriptase. Interacts with human APOBEC3F and APOBEC3G. Interacts with host UBCE7IP1 isoform 3/ZIN and possibly with SAT. Interacts with host tyrosine kinases HCK and FYN; these interactions may decrease level of phosphorylated APOBEC3G incorporation into virions. Interacts with host ABCE1; this interaction may play a role in protecting viral RNA from damage during viral assembly. Forms an E3 ligase complex by interacting with host CUL5 and elongin BC complex (ELOB and ELOC). Interacts with host MDM2; this interaction targets Vif for degradation by the proteasome.UniRule annotation

Family & Domainsi


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Regioni14 – 17Interaction with host APOBEC3F; F1-boxUniRule annotation4
Regioni40 – 44Interaction with host APOBEC3G; G-boxUniRule annotation5
Regioni54 – 72Interaction with host APOBEC3F and APOBEC3G; FG-boxUniRule annotationAdd BLAST19
Regioni74 – 79Interaction with host APOBEC3F; F2-boxUniRule annotation6
Regioni75 – 114RNA-bindingUniRule annotationAdd BLAST40
Regioni151 – 164MultimerizationUniRule annotationAdd BLAST14
Regioni171 – 172Membrane associationUniRule annotation2


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Motifi108 – 139HCCH motifUniRule annotationAdd BLAST32
Motifi144 – 153BC-box-like motifUniRule annotation10


The BC-like-box motif mediates the interaction with elongin BC complex.UniRule annotation
The HCCH motif (H-x5-C-x(18)-C-x5-H) mediates the interaction with CUL5.UniRule annotation

Sequence similaritiesi

Belongs to the primate lentivirus group Vif protein family.UniRule annotationSAAS annotation

Family and domain databases

HAMAPiMF_04081. HIV_VIF. 1 hit.
InterProiView protein in InterPro
IPR000475. Viral_infect.
PfamiView protein in Pfam
PF00559. Vif. 1 hit.


Sequence statusi: Complete.

Sequence processingi: The displayed sequence is further processed into a mature form.

O55981-1 [UniParc]FASTAAdd to basket

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160 170 180 190
Mass (Da):22,531
Last modified:June 1, 1998 - v1

Sequence databases

Select the link destinations:
Links Updated
AF019485 Genomic DNA. Translation: AAC02360.1.

Similar proteinsi

Entry informationi

Entry nameiO55981_9HIV1
AccessioniPrimary (citable) accession number: O55981
Entry historyiIntegrated into UniProtKB/TrEMBL: June 1, 1998
Last sequence update: June 1, 1998
Last modified: February 28, 2018
This is version 81 of the entry and version 1 of the sequence. See complete history.
Entry statusiUnreviewed (UniProtKB/TrEMBL)