View source for 6urw


==Crystal structure of ricin A chain in complex with inhibitor 4-(2-thienylmethyl)benzoic acid==
<StructureSection load='6urw' size='340' side='right'caption='[[6urw]], [[Resolution|resolution]] 2.40&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6urw]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Ricinus_communis Ricinus communis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6URW OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6URW 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]] 2.4&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=DMS:DIMETHYL+SULFOXIDE'>DMS</scene>, <scene name='pdbligand=EDO:1,2-ETHANEDIOL'>EDO</scene>, <scene name='pdbligand=R7T:4-[(thiophen-2-yl)methyl]benzoic+acid'>R7T</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=6urw FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6urw OCA], [https://pdbe.org/6urw PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6urw RCSB], [https://www.ebi.ac.uk/pdbsum/6urw PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6urw ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/RICI_RICCO RICI_RICCO] Ricin is highly toxic to animal cells and to a lesser extent to plant cells. The A chain acts as a glycosidase that removes a specific adenine residue from an exposed loop of the 28S rRNA (A4324 in mammals), leading to rRNA breakage. As this loop is involved in elongation factor binding, modified ribosomes are catalytically inactive and unable to support protein synthesis. The A chain can inactivate a few thousand ribosomes per minute, faster than the cell can make new ones. Therefore a single A chain molecule can kill an animal cell. The B chain binds to beta-D-galactopyranoside moieties on cell surface glycoproteins and glycolipids and facilitates the entry into the cell of the A chain; B chains are also responsible for cell agglutination (Lectin activity).
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== Publication Abstract from PubMed ==
Ricin toxin A subunit (RTA) removes an adenine from the universally conserved sarcin/ricin loop (SRL) on eukaryotic ribosomes, thereby inhibiting protein synthesis. No high affinity and selective small molecule therapeutic antidotes have been reported against ricin toxicity. RTA binds to the ribosomal P stalk to access the SRL. The interaction anchors RTA to the P protein C-termini at a well-defined hydrophobic pocket, which is on the opposite face relative to the active site. The RTA ribosome binding site has not been previously targeted by small molecule inhibitors. We used fragment screening with surface plasmon resonance to identify small molecular weight lead compounds that bind RTA and defined their interactions by crystallography. We identified five fragments, which bound RTA with mid-micromolar affinity. Three chemically distinct binding fragments were cocrystallized with RTA, and crystal structures were solved. Two fragments bound at the P stalk binding site, and the third bound to helix D, a motif distinct from the P stalk binding site. All fragments bound RTA remote from the catalytic site and caused little change in catalytic site geometry. Two fragments uniquely bound at the hydrophobic pocket with affinity sufficient to inhibit the catalytic activity on eukaryotic ribosomes in the low micromolar range. The binding mode of these inhibitors mimicked the interaction of the P stalk peptide, establishing that small molecule inhibitors can inhibit RTA binding to the ribosome with the potential for therapeutic intervention.

Small Molecule Inhibitors Targeting the Interaction of Ricin Toxin A Subunit with Ribosomes.,Li XP, Harijan RK, Kahn JN, Schramm VL, Tumer NE ACS Infect Dis. 2020 Jun 8. doi: 10.1021/acsinfecdis.0c00127. PMID:32428396<ref>PMID:32428396</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 6urw" style="background-color:#fffaf0;"></div>

==See Also==
*[[Ricin 3D structures|Ricin 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Ricinus communis]]
[[Category: Almo SC]]
[[Category: Bonanno JB]]
[[Category: Harijan RK]]
[[Category: Li XP]]
[[Category: Schramm VL]]
[[Category: Tumer NE]]