3kkr

Structural highlights

Function

[POL_BIV29] Matrix protein p16 forms the outer shell of the core of the virus, lining the inner surface of the viral membrane. Capsid protein p26 forms the conical core of the virus that encapsulates the genomic RNA-nucleocapsid complex. Interaction between incoming particle-associated Gag proteins and host dynein allows intracellular microtubule-dependent virus transport toward the perinuclear region, prior to nucleus translocation and integration into host genome.^[1] The aspartyl protease mediates proteolytic cleavages of Gag and Gag-Pol polyproteins during or shortly after the release of the virion from the plasma membrane. Cleavages take place as an ordered, step-wise cascade to yield mature proteins. This process is called maturation. Displays maximal activity during the budding process just prior to particle release from the cell.[PROSITE-ProRule:PRU00275] Reverse transcriptase/ribonuclease H (RT) is a multifunctional enzyme that converts the viral RNA genome into dsDNA in the cytoplasm, shortly after virus entry into the cell. This enzyme displays a DNA polymerase activity that can copy either DNA or RNA templates, and a ribonuclease H (RNase H) activity that cleaves the RNA strand of RNA-DNA heteroduplexes in a partially processive 3' to 5' endonucleasic mode. Conversion of viral genomic RNA into dsDNA requires many steps. A tRNA binds to the primer-binding site (PBS) situated at the 5'-end of the viral RNA. RT uses the 3' end of the tRNA primer to perform a short round of RNA-dependent minus-strand DNA synthesis. The reading proceeds through the U5 region and ends after the repeated (R) region which is present at both ends of viral RNA. The portion of the RNA-DNA heteroduplex is digested by the RNase H, resulting in a ssDNA product attached to the tRNA primer. This ssDNA/tRNA hybridizes with the identical R region situated at the 3' end of viral RNA. This template exchange, known as minus-strand DNA strong stop transfer, can be either intra- or intermolecular. RT uses the 3' end of this newly synthesized short ssDNA to perform the RNA-dependent minus-strand DNA synthesis of the whole template. RNase H digests the RNA template except for a polypurine tract (PPT) situated at the 5'-end of the genome. It is not clear if both polymerase and RNase H activities are simultaneous. RNase H probably can proceed both in a polymerase-dependent (RNA cut into small fragments by the same RT performing DNA synthesis) and a polymerase-independent mode (cleavage of remaining RNA fragments by free RTs). Secondly, RT performs DNA-directed plus-strand DNA synthesis using the PPT that has not been removed by RNase H as primer. PPT and tRNA primers are then removed by RNase H. The 3' and 5' ssDNA PBS regions hybridize to form a circular dsDNA intermediate. Strand displacement synthesis by RT to the PBS and PPT ends produces a blunt ended, linear dsDNA copy of the viral genome that includes long terminal repeats (LTRs) at both ends (By similarity). Integrase catalyzes viral DNA integration into the host chromosome, by performing a series of DNA cutting and joining reactions. This enzyme activity takes place after virion entry into a cell and reverse transcription of the RNA genome in dsDNA (By similarity).

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

See Also

• Integrase
• Retroviral Integrase

References

1. ↑ Su Y, Qiao W, Guo T, Tan J, Li Z, Chen Y, Li X, Li Y, Zhou J, Chen Q. Microtubule-dependent retrograde transport of bovine immunodeficiency virus. Cell Microbiol. 2010 Aug;12(8):1098-107. doi: 10.1111/j.1462-5822.2010.01453.x., Epub 2010 Feb 9. PMID:20148896 doi:http://dx.doi.org/10.1111/j.1462-5822.2010.01453.x
2. ↑ Yao X, Fang S, Qiao W, Geng Y, Shen Y. Crystal structures of catalytic core domain of BIV integrase: implications for the interaction between integrase and target DNA. Protein Cell. 2010 Apr;1(4):363-70. Epub 2010 May 8. PMID:21203948 doi:10.1007/s13238-010-0047-5