View source for 4imv


==Ricin A-chain variant 1-33/44-198 with engineered disulfide bond, R48C/T77C/D75N==
<StructureSection load='4imv' size='340' side='right'caption='[[4imv]], [[Resolution|resolution]] 2.25&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4imv]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Ricinus_communis Ricinus communis]. The May 2013 RCSB PDB [https://pdb.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/index.html Molecule of the Month] feature on ''Ricin''  by David Goodsell is [https://dx.doi.org/10.2210/rcsb_pdb/mom_2013_5 10.2210/rcsb_pdb/mom_2013_5]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4IMV OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4IMV 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]] 2.25&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=SO4:SULFATE+ION'>SO4</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=4imv FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4imv OCA], [https://pdbe.org/4imv PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4imv RCSB], [https://www.ebi.ac.uk/pdbsum/4imv PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4imv 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 ==
Vitetta and colleagues identified and characterized a putative vascular leak peptide (VLP) consensus sequence in recombinant ricin toxin A-chain (RTA) that contributed to dose-limiting human toxicity when RTA was administered intravenously in large quantities during chemotherapy. We disrupted this potentially toxic site within the more stable RTA1-33/44-198 vaccine immunogen and determined the impact of these mutations on protein stability, structure and protective immunogenicity using an experimental intranasal ricin challenge model in BALB/c mice to determine if the mutations were compatible. Single amino acid substitutions at the positions corresponding with RTA D75 (to A, or N) and V76 (to I, or M) had minor effects on the apparent protein melting temperature of RTA1-33/44-198 but all four variants retained greater apparent stability than the parent RTA. Moreover, each VLP(-) variant tested provided protection comparable with that of RTA1-33/44-198 against supralethal intranasal ricin challenge as judged by animal survival and several biomarkers. To understand better how VLP substitutions and mutations near the VLP site impact epitope structure, we introduced a previously described thermal stabilizing disulfide bond (R48C/T77C) along with the D75N or V76I substitutions in RTA1-33/44-198. The D75N mutation was compatible with the adjacent stabilizing R48C/T77C disulfide bond and the T(m) was unaffected, whereas the V76I mutation was less compatible with the adjacent disulfide bond involving C77. A crystal structure of the RTA1-33/44-198 R48C/T77C/D75N variant showed that the structural integrity of the immunogen was largely conserved and that a stable immunogen could be produced from E. coli. We conclude that it is feasible to disrupt the VLP site in RTA1-33/44-198 with little or no impact on apparent protein stability or protective efficacy in mice and such variants can be stabilized further by introduction of a disulfide bond.

Disruption of the Putative Vascular Leak Peptide Sequence in the Stabilized Ricin Vaccine Candidate RTA1-33/44-198.,Janosi L, Compton JR, Legler PM, Steele KE, Davis JM, Matyas GR, Millard CB Toxins (Basel). 2013 Jan 30;5(2):224-48. doi: 10.3390/toxins5020224. PMID:23364220<ref>PMID:23364220</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 4imv" style="background-color:#fffaf0;"></div>

==See Also==
*[[Ricin 3D structures|Ricin 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: RCSB PDB Molecule of the Month]]
[[Category: Ricin]]
[[Category: Ricinus communis]]
[[Category: Compton JR]]
[[Category: Legler PM]]
[[Category: Millard CB]]