CA - P24, Core Antigen capsid protein

HIV CA forms the conical core of the viral particle.

PDB-1TAM: HIV-1 (isolate UNKNOWN) Matrix protein - produced using SwissModel/SPDBV/POVray

Key web links:
ViralZone: HIV-1, HIV replication cycle, HIV resource
PDB: 1E6J (HIV-1 CA)
UniProt: P04591 (HIV-1 HXB2 GAG)
Chime Tutorial: not available
HIV-1/Human Protein Interaction DB: HIV-1 Gag
Los Alamos HIV structure DB: Core Antigen Capsid
EMBL: K03455 [EMBL/GenBank/DDBJ]


  • p24 (231 amino acids)

Cleavage sites:


  • Forms a cone-shaped shell that encapsulates the genomic RNA-nucleocapsid complex and mediates the delivery of this complex into the host nucleus .


  • Virion
  • Cell Cytoplasm

Additional Information:

  • Late timing of expression.
  • CA is phosphorylated.
  • Disruption of the CA/Cyclophilin A interaction leads to the inhibition of viral replication .
  • The HIV capsid is made of twelve pentameric and over a hundred hexameric CA rings (1000-1500 molecules) .

Gag-Ca Function & Host-Virus Protein Interactions:[TOP]

Interactions highlighted in the image:

Potential interactions (not in the image):

Genomic Location & Protein Sequence: [TOP]

HIV-1 (HXB2):

          10         20         30         40         50         60         70         80         90        100
| | | | | | | | | |
110 120 130 140 150 160 170 180 190 200
| | | | | | | | | |
210 220 230
| | |
[download in fasta format]

Length: 231 amino acids
Molecular Weight: 25579 Da
Theoretical pI: 6.26
Position relative to Gag protein: 133 - 500

Protein Domains/Folds/Motifs: [TOP]

InterPro signature for Retrovirus capsid, C-terminal - IPR008916

InterPro signature for Retrovirus capsid, N-terminal core - IPR008919

Secondary Structure prediction:

Antigenic Sites - EMBOSS:

Predicted Motifs: Printer-friendly version

Protein kinase C:
Casein kinase II:
Tyrosine kinase:
cAMP / cGMP kinase:
Cell attachment motif:
Asp Protease motif:
Asp Prot Retro motif:
Cysteine-rich Region:
Tryptophan-rich Region:
Zinc-finger CCHC motif:
Leucine Zipper motif:

Primary and Secondary Database Entries: [TOP]


ViralZone: HIV-1, HIV replication cycle, HIV resource
PDB/MMDB: Search for HIV-1 & Capsid

UniProt: P04591 (HIV-1 HXB2 GAG)
EMBL: K03455; AAB50258.1 [EMBL/GenBank/DDBJ]

InterPro: IPR008916 - Retroviral Core Antigen C-terminal Domain / IPR008919 - Retroviral Core Antigen N-terminal Core Domain
Pfam: PF00607
Prints: none
SCOP: SSF47943 Retroviral Core Antigen N-terminus / SSF47353 Retroviral Core Antigen N-terminus
BLOCKS: P04591
Prosite: P04591
ProtoNet: P04591
Database of Interacting Proteins: P04591
ModBase: P04591
HIV-1/Human Protein Interaction DB: HIV-1 Gag
HIV-1 Sequence Database Los Alamos HIV Sequence Database


Reviews and References: [TOP]

Cite the resource by citing the following paper:
Doherty R et al. BioAfrica's HIV-1 Proteomics Resource: Combining protein data with bioinformatics tools. Retrovirology (2005), 9;2(1):18.

1 - HIV Sequence Compendium 2000
Kuiken CL, Foley B, Hahn B, Korber B, Marx PA, McCutchan F, Mellors JW, Mullins JI, Sodroski J, Wolinksy S.
Theoretical Biol. & Biophys. Group, Los Alamos Nat Lab, LA-UR 01-3860 [Read it online: Compendium]
2 - Retroviruses
Coffin JM, Hughes SH, Varmus HE.
CD-ROM ed. (2002) Cold Spring Harbor Laboratory Press [Read it online: NCBI Bookshelf]
3 - Molecular Characteristics of HIV-1 Subtype C Viruses from KwaZulu-Natal, South Africa:
Implications for Vaccine and Antiretroviral Control Strategies.
Gordon M, De Oliveira T, Bishop K, Coovadia HM, Madurai L, Engelbrecht S, Janse van Rensburg E, Mosam A, Smith A, Cassol S.
Journal of Virology 77(4): 2587-2599 (2003) [pubmed: 12551997]
4 - Specific incorporation of cyclophilin A into HIV-1 virions.
Franke EK, Yuan HE, Luban J.
Nature 372: 359-362 (1994) [pubmed: 7969494]
5 - Functional association of cyclophilin A with HIV-1 virions.
Thali M, Bukovsky A, Kondo E.
Nature 372: 363-365 (1994) [pubmed: 7969495]
6 - Inhibition of HIV-1 replication by cyclosporine A or related compounds correlates with the ability
to disrupt the Gag-cyclophilin A interaction.
Franke EK, Luban J.
Virology 222: 279-282 (1996) [pubmed: 8806510]
7 - The structural biology of HIV assembly.
Ganser-Pornillos BK, Yeager M, Sundquist WI.
Curr Opin Struct Biol. 18(2):203-17 (2008) [pubmed: 18406133]
8 - Mature HIV-1 capsid structure by cryo-electron microscopy and all-atom molecular dynamics.
Zhao G, Perilla JR, Yufenyuy EL, Meng X, Chen B, Ning J, Ahn J, Gronenborn AM, Schulten K, Aiken C, Zhang P.
Nature 497(7451):643-6 (2013) [pubmed: 23719463]
9 - A model for cofactor use during HIV-1 reverse transcription and nuclear entry.
Hilditch L, Towers GJ.
Curr Opin Virol. 4:32-6 (2014) [pubmed: 24525292]
10 - Crystal structure of human cyclophilin A bound to the amino-terminal domain of HIV-1 capsid.
Gamble TR, Vajdos FF, Yoo S, Worthylake DK, Houseweart M, Sundquist WI, Hill CP.
Cell 87(7):1285-94 (1996) [pubmed: 8980234]
11 - Uncoating of human immunodeficiency virus type 1 requires prolyl isomerase Pin1.
Misumi S, Inoue M, Dochi T, Kishimoto N, Hasegawa N, Takamune N, Shoji S.
J Biol Chem. 285(33):25185-95 (2010) [pubmed: 20529865]
12 - HIV-1 capsid-cyclophilin interactions determine nuclear import pathway, integration targeting and replication efficiency.
Schaller T, Ocwieja KE, Rasaiyaah J, Price AJ, Brady TL, Roth SL, Hué S, Fletcher AJ, Lee K, KewalRamani VN, Noursadeghi M, Jenner RG, James LC, Bushman FD, Towers GJ.
PLoS Pathog. 7(12):e1002439 (2011) [pubmed: 22174692]
13 - Nup153 and Nup98 bind the HIV-1 core and contribute to the early steps of HIV-1 replication.
Di Nunzio F, Fricke T, Miccio A, Valle-Casuso JC, Perez P, Souque P, Rizzi E, Severgnini M, Mavilio F, Charneau P, Diaz-Griffero F.
Virology 440(1):8-18 (2013) [pubmed: 23523133]
14 - CPSF6 defines a conserved capsid interface that modulates HIV-1 replication.
Price AJ, Fletcher AJ, Schaller T, Elliott T, Lee K, KewalRamani VN, Chin JW, Towers GJ, James LC.
PLoS Pathog. 8(8):e1002896 (2012) [pubmed: 22956906]
15 - Specific recognition and accelerated uncoating of retroviral capsids by the TRIM5alpha restriction factor.
Stremlau M, Perron M, Lee M, Li Y, Song B, Javanbakht H, Diaz-Griffero F, Anderson DJ, Sundquist WI, Sodroski J.
Proc Natl Acad Sci U S A. 103(14):5514-9 (2006) [pubmed: 16540544]

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Page last updated by Megan Druce, Paula Sommer and Tulio de Oliveira (UKZN/Africa Centre) & Philippe Le Mercier, Chantal Hulo and Patrick Masson (SIB/ViralZone).