UniProt functional annotation for P03355

UniProt code: P03355.

Organism: Moloney murine leukemia virus (isolate Shinnick) (MoMLV).
Taxonomy: Viruses; Riboviria; Pararnavirae; Artverviricota; Revtraviricetes; Ortervirales; Retroviridae; Orthoretrovirinae; Gammaretrovirus; Murine leukemia virus.
 
Function: [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-Pol, or to Gag-Pol binding host factors. Interaction with HECT ubiquitin ligases probably links the viral protein to the host ESCRT pathway and facilitates release. {ECO:0000250|UniProtKB:P03332}.
 
Function: [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 pre-integration complex. {ECO:0000250|UniProtKB:P03332}.
 
Function: [RNA-binding phosphoprotein p12]: Constituent of the pre- integration complex (PIC) which tethers the latter to mitotic chromosomes. This allows the integration of the viral genome into the host DNA. {ECO:0000269|PubMed:21085616, ECO:0000269|PubMed:23300449}.
 
Function: [Capsid protein p30]: Forms the spherical core of the virion that encapsulates the genomic RNA-nucleocapsid complex. {ECO:0000250|UniProtKB:P03336}.
 
Function: [Nucleocapsid protein p10-Pol]: Involved in the packaging and encapsidation of two copies of the genome (By similarity). Binds with high affinity to conserved UCUG elements within the packaging signal, located near the 5'-end of the genome (By similarity). This binding is dependent on genome dimerization (By similarity). Acts as a nucleic acid chaperone which is involved in rearrangement of nucleic acid secondary structures during gRNA retrotranscription (PubMed:25209668). {ECO:0000250|UniProtKB:P03332, ECO:0000269|PubMed:25209668}.
 
Function: [Protease]: 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 (Potential). Cleaves the translation initiation factor eIF4G leading to the inhibition of host cap-dependent translation (PubMed:14610163). {ECO:0000255|PROSITE- ProRule:PRU00275, ECO:0000269|PubMed:14610163}.
 
Function: [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. {ECO:0000255}.
 
Function: [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. {ECO:0000305|PubMed:11559787, ECO:0000305|PubMed:17003051}.
 
Catalytic activity: Reaction=a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1); Xref=Rhea:RHEA:22508, Rhea:RHEA-COMP:11130, Rhea:RHEA-COMP:11131, ChEBI:CHEBI:33019, ChEBI:CHEBI:61560, ChEBI:CHEBI:83828; EC=2.7.7.49; Evidence={ECO:0000255|PROSITE- ProRule:PRU00405};
Catalytic activity: Reaction=a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1); Xref=Rhea:RHEA:22508, Rhea:RHEA-COMP:11130, Rhea:RHEA-COMP:11131, ChEBI:CHEBI:33019, ChEBI:CHEBI:61560, ChEBI:CHEBI:83828; EC=2.7.7.7; Evidence={ECO:0000255|PROSITE- ProRule:PRU00405};
Catalytic activity: Reaction=Endonucleolytic cleavage to 5'-phosphomonoester.; EC=3.1.26.4; Evidence={ECO:0000255|PROSITE-ProRule:PRU00408};
Cofactor: Name=Mg(2+); Xref=ChEBI:CHEBI:18420; Evidence={ECO:0000255|PROSITE-ProRule:PRU00405}; Note=The RT polymerase active site binds 2 magnesium ions. {ECO:0000255|PROSITE-ProRule:PRU00405};
Cofactor: Name=Mg(2+); Xref=ChEBI:CHEBI:18420; Evidence={ECO:0000305}; Note=Binds 1 magnesium ion for ribonuclease H (RNase H) activity. {ECO:0000269|PubMed:16912289};
Cofactor: Name=Mg(2+); Xref=ChEBI:CHEBI:18420; Evidence={ECO:0000305}; Note=Magnesium ions are required for integrase activity. Binds at least 1, maybe 2 magnesium ions. {ECO:0000305};
Activity regulation: [Protease]: Most efficiently inhibited by Amprenavir, which is able to block Gag-Pol processing in infected cells. {ECO:0000269|PubMed:16603535}.
Biophysicochemical properties: pH dependence: Optimum pH is 5.0 for protease activity. {ECO:0000269|PubMed:16603535};
Subunit: [Capsid protein p30]: Homohexamer; further associates as homomultimer (By similarity). The virus core is composed of a lattice formed from hexagonal rings, each containing six capsid monomers (PubMed:12093170). Interacts with mouse UBE2I and mouse PIAS4 (PubMed:16352559). {ECO:0000250|UniProtKB:P03336, ECO:0000269|PubMed:12093170, ECO:0000269|PubMed:16352559}.
Subunit: [Gag-Pol polyprotein]: Interacts (via PPXY motif) with host NEDD4 (PubMed:15908698). Interacts (via PSAP motif) with host TSG101 (PubMed:15908698). Interacts (via LYPX(n)L motif) with host PDCD6IP (PubMed:15908698). {ECO:0000269|PubMed:15908698}.
Subunit: [Reverse transcriptase/ribonuclease H]: The reverse transcriptase is a monomer (Potential). Interacts (via RNase domains) with host release factor ETF1; this interaction is essential for translational readthrough of amber codon between viral gag and pol genes, as well as for viral replication (PubMed:14636559, PubMed:27329342). {ECO:0000269|PubMed:14636559, ECO:0000269|PubMed:27329342}.
Subunit: [Integrase]: Homodimer (PubMed:14599799). {ECO:0000269|PubMed:14599799}.
Subcellular location: [Gag-Pol polyprotein]: Virion {ECO:0000250|UniProtKB:P03332}. Host cell membrane {ECO:0000250|UniProtKB:P03332}; Lipid-anchor {ECO:0000250|UniProtKB:P03332}. Host late endosome membrane {ECO:0000250|UniProtKB:P03332}; Lipid-anchor {ECO:0000250|UniProtKB:P03332}. Host endosome, host multivesicular body {ECO:0000250|UniProtKB:P26807}. Note=These locations are probably linked to virus assembly sites. {ECO:0000305}.
Subcellular location: [Matrix protein p15]: Virion {ECO:0000305}.
Subcellular location: [Capsid protein p30]: Virion {ECO:0000305}.
Subcellular location: [Nucleocapsid protein p10-Pol]: Virion {ECO:0000305}.
Subcellular location: [Protease]: Virion {ECO:0000269|PubMed:16603535}.
Subcellular location: [RNA-binding phosphoprotein p12]: Host cytoplasm {ECO:0000269|PubMed:21085616, ECO:0000269|PubMed:23300449}. Note=Localizes to the host cytoplasm early in infection and binds to the mitotic chromosomes later on. {ECO:0000269|PubMed:21085616, ECO:0000269|PubMed:23300449}.
Domain: [Gag-Pol polyprotein]: 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. {ECO:0000250|UniProtKB:P03332}.
Ptm: [Gag-Pol polyprotein]: Ubiquitinated by ITCH. Gag can recruit the ubiquitin ligase Itch in an L domain-independent manner to facilitate virus release via a mechanism that involves Gag ubiquitination. {ECO:0000250|UniProtKB:P03332}.
Ptm: [Gag-Pol polyprotein]: Specific enzymatic cleavages by the viral protease yield mature proteins. The protease is released by autocatalytic cleavage. The polyprotein is cleaved during and after budding, this process is termed maturation. {ECO:0000269|PubMed:16603535}.
Ptm: [Capsid protein p30]: Sumoylated; which is required for virus replication. {ECO:0000269|PubMed:16352559}.
Ptm: [RNA-binding phosphoprotein p12]: Phosphorylated on serine residues. {ECO:0000269|PubMed:12525616}.
Miscellaneous: [Gag-Pol polyprotein]: This protein is translated as a gag-pol fusion protein by episodic readthrough of the gag protein termination codon. Readthrough of the terminator codon TAG occurs between the codons for 538-Asp and 540-Gly. {ECO:0000269|PubMed:27329342, ECO:0000269|PubMed:3885215}.
Miscellaneous: [Nucleocapsid protein p10-Pol]: Nucleocapsid protein p10-Pol released from Pol polyprotein (NC-pol) is a few amino acids shorter than the nucleocapsid protein p10 released from Gag polyprotein (NC-gag). {ECO:0000305}.
Miscellaneous: [Reverse transcriptase/ribonuclease H]: The reverse transcriptase is an error-prone enzyme that lacks a proof-reading function. High mutations rate is a direct consequence of this characteristic. RT also displays frequent template swiching leading to high recombination rate. Recombination mostly occurs between homologous regions of the two copackaged RNA genomes. If these two RNA molecules derive from different viral strains, reverse transcription will give rise to highly recombinated proviral DNAs. {ECO:0000255|PROSITE- ProRule:PRU00405}.

Annotations taken from UniProtKB at the EBI.