View source for 3mk9

==Stabilized Ricin Immunogen 1-33/44-198==
<StructureSection load='3mk9' size='340' side='right' caption='[[3mk9]], [[Resolution|resolution]] 2.08&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[3mk9]] is a 1 chain structure with sequence from [http://en.wikipedia.org/wiki/Ricinus_communis Ricinus communis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3MK9 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=3MK9 FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[3lc9|3lc9]]</td></tr>
<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/rRNA_N-glycosylase rRNA N-glycosylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.2.22 3.2.2.22] </span></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=3mk9 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3mk9 OCA], [http://www.rcsb.org/pdb/explore.do?structureId=3mk9 RCSB], [http://www.ebi.ac.uk/pdbsum/3mk9 PDBsum]</span></td></tr>
</table>
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== Publication Abstract from PubMed ==
RTA1-33/44-198 is a catalytically inactive, single-domain derivative of the ricin toxin A-chain (RTA) engineered to serve as a stable protein scaffold for presentation of native immunogenic epitopes (Olson et al., Protein Eng Des Sel 2004;17:391-397). To improve the stability and solubility of RTA1-33/44-198 further, we have undertaken the design challenge of introducing a disulfide (SS) bond. Nine pairs of residues were selected for placement of the SS-bond based on molecular dynamics simulation studies of the modeled single-domain chain. Disulfide formation at either of two positions (R48C/T77C or V49C/E99C) involving a specific surface loop (44-55) increased the protein melting temperature by ~5 degrees C compared with RTA1-33/44-198 and by ~13 degrees C compared with RTA. Prolonged stability studies of the R48C/T77C variant (&gt; 60 days at 37 degrees C, pH 7.4) confirmed a &gt; 40% reduction in self-aggregation compared with RTA1-33/44-198 lacking the SS-bond. The R48C/T77C variant retained affinity for anti-RTA antibodies capable of neutralizing ricin toxin, including a monoclonal that recognizes a human B-cell epitope. Introduction of either R48C/T77C or V49C/E99C promoted crystallization of RTA1-33/44-198, and the X-ray structures of the variants were solved to 2.3 A or 2.1 A resolution, respectively. The structures confirm formation of an intramolecular SS-bond, and reveal a single-domain fold that is significantly reduced in volume compared with RTA. Loop 44 to 55 is partly disordered as predicted by simulations, and is positioned to form self-self interactions between symmetry-related molecules. We discuss the importance of RTA loop 34 to 55 as a nucleus for unfolding and aggregation, and draw conclusions for ongoing structure-based minimalist design of RTA-based immunogens.

Introduction of a disulfide bond leads to stabilization and crystallization of a ricin immunogen.,Compton JR, Legler PM, Clingan BV, Olson MA, Millard CB Proteins. 2011 Apr;79(4):1048-60. doi: 10.1002/prot.22933. Epub 2011 Jan, 5. PMID:21387408<ref>PMID:21387408</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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==See Also==
*[[Ricin|Ricin]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Ricinus communis]]
[[Category: RRNA N-glycosylase]]
[[Category: Compton, J R]]
[[Category: Legler, P M]]
[[Category: Millard, C B]]
[[Category: Disulfide bond]]
[[Category: Hydrolase]]
[[Category: Immunogen]]
[[Category: Nucleotide-binding]]
[[Category: Plant defense]]
[[Category: Protein synthesis inhibitor]]
[[Category: Toxin]]