Gag-Pol polyprotein - P03355 (POL_MLVMS)


Protein Feature View of PDB entries mapped to a UniProtKB sequence  

  • Number of PDB entries for P03355: 35
Gag-Pol polyprotein plays a role in budding and is processed by the viral protease during virion maturation outside the cell. During budding, it recruits, in a PPXY-dependent or independent manner, Nedd4-like ubiquitin ligases that conjugate ubiquitin molecules to Gag, or to Gag binding host factors. Interaction with HECT ubiquitin ligases probably link the viral protein to the host ESCRT pathway and facilitate release. (data source: UniProt  )
Matrix protein p15 targets Gag and gag-pol polyproteins to the plasma membrane via a multipartite membrane binding signal, that includes its myristoylated N-terminus. Also mediates nuclear localization of the preintegration complex. (data source: UniProt  )

Capsid protein p30 forms the spherical core of the virion that encapsulates the genomic RNA-nucleocapsid complex. (data source: UniProt  )
Nucleocapsid protein p10 is involved in the packaging and encapsidation of two copies of the genome. Binds with high affinity to conserved UCUG elements within the packaging signal, located near the 5'-end of the genome. This binding is dependent on genome dimerization. (data source: UniProt  )
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. (data source: UniProt  )
Reverse transcriptase/ribonuclease H (RT) is a multifunctional enzyme that converts the viral dimeric 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 primers. 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. (data source: UniProt  )
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. The first step in the integration process is 3' processing. This step requires a complex comprising the viral genome, matrix protein and integrase. This complex is called the pre-integration complex (PIC). The integrase protein removes 2 nucleotides from each 3' end of the viral DNA, leaving recessed CA OH's at the 3' ends. In the second step that requires cell division, the PIC enters cell nucleus. In the third step, termed strand transfer, the integrase protein joins the previously processed 3' ends to the 5' ends of strands of target cellular DNA at the site of integration. The last step is viral DNA integration into host chromosome. (data source: UniProt  )
Catalytic Activity

Endonucleolytic cleavage to 5'-phosphomonoester.

(data source: UniProt  )
Subunit structure
Capsid protein p30 is a homohexamer, that further associates as homomultimer. The virus core is composed of a lattice formed from hexagonal rings, each containing six capsid monomers. The protease is a homodimer, whose active site consists of two apposed aspartic acid residues. The reverse transcriptase is a monomer (By similarity). Capsid protein p30 interacts with mouse UBE2I and mouse PIAS4. Reverse transcriptase/ribonuclease H p80 interacts (via RT and RNase domains) with host release factor ETF1; this interaction is essential for translational readthrough of amber codon between viral gag and pol genes. Gag-Pol polyprotein also interacts with host release factor ETF1. (data source: UniProt  )
Late-budding domains (L domains) are short sequence motifs essential for viral particle release. They can occur individually or in close proximity within structural proteins. They interacts with sorting cellular proteins of the multivesicular body (MVB) pathway. Most of these proteins are class E vacuolar protein sorting factors belonging to ESCRT-I, ESCRT-II or ESCRT-III complexes. RNA-binding phosphoprotein p12 contains one L domain: a PPXY motif which potentially interacts with the WW domain 3 of NEDD4 E3 ubiquitin ligase. PPXY motif is essential for virus egress. Matrix protein p15 contains one L domain: a PTAP/PSAP motif, which potentially interacts with the UEV domain of TSG101. The junction between the matrix protein p15 and RNA-binding phosphoprotein p12 also contains one L domain: a LYPX(n)L motif which potentially interacts with PDCD6IP. Both PSAP and LYPX(n)L domains might play little to no role in budding and possibly drive residual virus release. contains. (data source: UniProt  )
This protein in other organisms (by gene name):
Organism (common name): isolate Shinnick
Other Gene name: gag-pol
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