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Title: Integrase  
Author: World Heritage Encyclopedia
Language: English
Subject: HIV, Reverse transcriptase, Discovery and development of integrase inhibitors, Retrovirus, Cre-Lox recombination
Collection: Enzymes, Viral Enzymes, Virology
Publisher: World Heritage Encyclopedia


Integrase Zinc binding domain
solution structure of the n-terminal zn binding domain of hiv-1 integrase (e form), nmr, 38 structures
Symbol Integrase_Zn
Pfam PF02022
InterPro IPR003308
SCOP 1wjb
Integrase core domain
crystal structure of rsv two-domain integrase
Symbol rve
Pfam PF00665
Pfam clan CL0219
InterPro IPR001584
SCOP 2itg
Integrase DNA binding domain
crystal structure of rsv two-domain integrase
Symbol IN_DBD_C
Pfam PF00552
InterPro IPR001037
SCOP 1ihw

Retroviral integrase (IN) is an enzyme produced by a retrovirus (such as HIV) that enables its genetic material to be integrated into the DNA of the infected cell. Retroviral INs are not to be confused with phage integrases, such as λ phage integrase (Int) (see site-specific recombination).

IN is a key component in the retroviral pre-integration complex (PIC).


  • Structure 1
  • Function 2
  • HIV IN 3
  • See also 4
  • References 5
  • External links 6


All retroviral IN proteins contain three canonical domains, connected by flexible linkers:

  • an N-terminal HH-CC zinc-binding domain (a three-helical bundle stabilised by coordination of a Zn(II) cation)
  • a catalytic core domain (RNaseH fold)
  • a C-terminal DNA-binding domain (SH3 fold)[1]

Crystal and NMR structures of the individual domains and 2-domain constructs of integrases from HIV-1, HIV-2, SIV, and Rous Sarcoma Virus (RSV) have been reported, with the first structures determined in 1994.

Biochemical data and structural data suggest that retroviral IN functions as a tetramer (dimer-of-dimers). All three domains are important for multimerisation and viral DNA binding. Early in 2010, scientists solved the crystal structure of IN from prototype foamy virus (PFV) assembled on viral DNA ends.[2]

In addition, several host cellular proteins have been shown to interact with IN to facilitate the integration process. Human chromatin-associated protein LEDGF, which tightly binds HIV IN and directs HIV PIC towards highly expressed genes for integration, is an example of such a host factor.


Integration occurs following production of the double-stranded viral DNA by the viral RNA/DNA-dependent DNA polymerase reverse transcriptase.

The main function of IN is to insert the viral DNA into the host chromosomal DNA, a step that is essential for HIV replication. Integration is a point of no return for the cell, which becomes a permanent carrier of the viral genome (provirus). Integration is in part responsible for the persistence of retroviral infections. After integration, the viral gene expression and particle production may take place immediately or at some point in the future. The timing, it is presumed, depends on the activity of the chromosomal locus hosting the provirus.

Retroviral IN catalyzes two reactions:

  • 3'-processing, in which two or three nucleotides are removed from one or both 3' ends of the viral DNA to expose the invariant CA dinucleotides at both 3'-ends of the viral DNA.
  • the strand transfer reaction, in which the processed 3' ends of the viral DNA are covalently ligated to the host chromosomal DNA.

Both reactions are catalysed by the same active site and occur via transesterification, without a covalent protein-DNA intermediate, in contrast to reactions catalysed by Ser and Tyr recombinases (see site specific recombination).


Here, HIV Integrase is shown in its full structure with its catalytic amino acids shown in ball and stick form.

HIV integrase is a 32 kDa protein produced from the C-terminal portion of the Pol gene product, and is an attractive target for new anti-HIV drugs.

In November 2005, data from a phase 2 study of an investigational HIV integrase inhibitor, MK-0518, demonstrated that the compound has potent antiviral activity.[3][4] On October 12, 2007, the Food and Drug Administration (U.S.) approved the integrase inhibitor Raltegravir (MK-0518, brand name Isentress TM).[5] The second integrase inhibitor, elvitegravir, was approved in the U.S. in August 2012.[6]

The crystal structure of human foamy virus integrase has been examined successfully.[7]

This protein may use the morpheein model of allosteric regulation.[8]

See also


  1. ^ Lodi PJ, Ernst JA, Kuszewski J, Hickman AB, Engelman A, Craigie R, Clore GM, Gronenborn AM (August 1995). "Solution structure of the DNA binding domain of HIV-1 integrase". Biochemistry 34 (31): 9826–33.  
  2. ^ "Scientists say crack HIV/AIDS puzzle for drugs". Reuters. January 31, 2010. 
  3. ^ Morales-Ramirez JO, Teppler H, Kovacs C, et al. Antiretroviral effect of MK-0518, a novel HIV-1 integrase inhibitor, in ART-naïve HIV-1 infected patients. Program and abstracts of the 10th European AIDS Conference; November 17–20, 2005; Dublin, Ireland. Abstract LBPS1/6. Online summary:
  4. ^ Savarino A (December 2006). "A historical sketch of the discovery and development of HIV-1 integrase inhibitors". Expert Opin Investig Drugs 15 (12): 1507–22.  
  5. ^ "FDA approves drug that fights HIV in new way -". CNN. October 12, 2007. Retrieved May 5, 2010. 
  6. ^ Sax PE, DeJesus E, Mills A, Zolopa A, Cohen C, Wohl D, Gallant JE, Liu HC, Zhong L, Yale K, White K, Kearney BP, Szwarcberg J, Quirk E, Cheng AK (June 2012). "Co-formulated elvitegravir, cobicistat, emtricitabine, and tenofovir versus co-formulated efavirenz, emtricitabine, and tenofovir for initial treatment of HIV-1 infection: a randomised, double-blind, phase 3 trial, analysis of results after 48 weeks". Lancet 379 (9835): 2439–48.  
  7. ^ Hare S, Gupta SS, Valkov E, Engelman A, Cherepanov P (March 2010). "Retroviral intasome assembly and inhibition of DNA strand transfer". Nature 464 (7286): 232–6.  
  8. ^ Selwood T, Jaffe EK (March 2012). "Dynamic dissociating homo-oligomers and the control of protein function". Arch. Biochem. Biophys. 519 (2): 131–43.  

External links

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