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==Poliovirus Polymerase - C290I Loop Mutant==
<StructureSection load='4nlo' size='340' side='right'caption='[[4nlo]], [[Resolution|resolution]] 2.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4nlo]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Human_poliovirus_1_Mahoney Human poliovirus 1 Mahoney]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4NLO OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4NLO FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.2&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=1PE:PENTAETHYLENE+GLYCOL'>1PE</scene>, <scene name='pdbligand=ACY:ACETIC+ACID'>ACY</scene>, <scene name='pdbligand=CAS:S-(DIMETHYLARSENIC)CYSTEINE'>CAS</scene>, <scene name='pdbligand=NA:SODIUM+ION'>NA</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=4nlo FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4nlo OCA], [https://pdbe.org/4nlo PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4nlo RCSB], [https://www.ebi.ac.uk/pdbsum/4nlo PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4nlo ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/POLG_POL1M POLG_POL1M] Capsid proteins VP1, VP2, VP3 and VP4 form a closed capsid enclosing the viral positive strand RNA genome. VP4 lies on the inner surface of the protein shell formed by VP1, VP2 and VP3. All the three latter proteins contain a beta-sheet structure called beta-barrel jelly roll. Together they form an icosahedral capsid (T=3) composed of 60 copies of each VP1, VP2, and VP3, with a diameter of approximately 300 Angstroms. VP1 is situated at the 12 fivefold axes, whereas VP2 and VP3 are located at the quasi-sixfold axes. The interaction of five VP1 proteins in the fivefold axes results in a prominent protusion extending to about 25 Angstroms from the capsid shell. The resulting structure appears as a steep plateau encircled by a valley or cleft. This depression also termed canyon is the receptor binding site. The capsid interacts with human PVR at this site to provide virion attachment to target cell. This attachment induces virion internalization predominantly through clathrin- and caveolin-independent endocytosis in Hela cells and through caveolin-mediated endocytosis in brain microvascular endothelial cells. VP4 and VP1 subsequently undergo conformational changes leading to the formation of a pore in the endosomal membrane, thereby delivering the viral genome into the cytoplasm.<ref>PMID:9755863</ref> <ref>PMID:15919927</ref> <ref>PMID:18191571</ref>   VP0 precursor is a component of immature procapsids (By similarity).<ref>PMID:9755863</ref> <ref>PMID:15919927</ref> <ref>PMID:18191571</ref>   Protein 2A is a cysteine protease that is responsible for the cleavage between the P1 and P2 regions. It cleaves the host translation initiation factor EIF4G1, in order to shut down the capped cellular mRNA transcription.<ref>PMID:9755863</ref> <ref>PMID:15919927</ref> <ref>PMID:18191571</ref>   Protein 2B affects membrane integrity and cause an increase in membrane permeability (By similarity).<ref>PMID:9755863</ref> <ref>PMID:15919927</ref> <ref>PMID:18191571</ref>   Protein 2C associates with and induces structural rearrangements of intracellular membranes. It displays RNA-binding, nucleotide binding and NTPase activities.<ref>PMID:9755863</ref> <ref>PMID:15919927</ref> <ref>PMID:18191571</ref>   Protein 3A, via its hydrophobic domain, serves as membrane anchor. It also inhibits endoplasmic reticulum-to-Golgi transport (By similarity).<ref>PMID:9755863</ref> <ref>PMID:15919927</ref> <ref>PMID:18191571</ref>   Protein 3C is a cysteine protease that generates mature viral proteins from the precursor polyprotein. In addition to its proteolytic activity, it binds to viral RNA, and thus influences viral genome replication. RNA and substrate bind co-operatively to the protease (By similarity).<ref>PMID:9755863</ref> <ref>PMID:15919927</ref> <ref>PMID:18191571</ref>   RNA-directed RNA polymerase 3D-POL replicates genomic and antigenomic RNA by recognizing replications specific signals (By similarity).<ref>PMID:9755863</ref> <ref>PMID:15919927</ref> <ref>PMID:18191571</ref> 
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== Publication Abstract from PubMed ==
The mechanism whereby RNA is translocated by the single subunit viral RNA-dependent RNA polymerases is not yet understood. These enzymes lack homologs of the "O-helix" structures and associated fingers domain movements thought to be responsible for translocation in many DNA-templated polymerases. The structures of multiple picornavirus polymerase elongation complexes suggest that these enzymes use a different molecular mechanism where translocation is not strongly coupled to the opening of the active site following catalysis. Here we present the 2.0-2.6 A resolution crystal structures and biochemical data for twelve poliovirus polymerase mutants that together show how proper enzyme function and translocation activity requires conformational flexibility of a loop sequence in the palm domain B-motif. Within the loop, the Ser288-Gly289-Cys290 sequence is shown to play a major role in the catalytic cycle based on RNA binding, processive elongation activity, and single nucleotide incorporation assays. The structures show that Ser288 forms a key hydrogen bond with Asp238, the backbone flexibility of Gly289 is require for translocation competency, and Cys290 modulates the overall elongation activity of the enzyme. Some conformations of the loop represent likely intermediates on the way to forming the catalytically competent closed active site, while others are consistent with a role in promoting translocation of the nascent base pair out of the active site. The loop structure and key residues surrounding it are highly conserved, suggesting the structural dynamics we observe in poliovirus 3Dpol are a common feature of viral RNA-dependent RNA polymerases.

Distinct Conformations of a Putative Translocation Element in Poliovirus Polymerase.,Sholders AJ, Peersen OB J Mol Biol. 2014 Jan 11. pii: S0022-2836(14)00020-5. doi:, 10.1016/j.jmb.2013.12.031. PMID:24424421<ref>PMID:24424421</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4nlo" style="background-color:#fffaf0;"></div>

==See Also==
*[[RNA polymerase 3D structures|RNA polymerase 3D structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Human poliovirus 1 Mahoney]]
[[Category: Large Structures]]
[[Category: Peersen OB]]
[[Category: Sholders AJ]]