View source for 3hex


==Cyclic residues in alpha/beta-peptide helix bundles: GCN4-pLI side chain sequence on an (alpha-alpha-beta) backbone with cyclic beta-residues at positions 1, 4, 19 and 28==
<StructureSection load='3hex' size='340' side='right'caption='[[3hex]], [[Resolution|resolution]] 2.80&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[3hex]] is a 1 chain structure. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3HEX OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=3HEX 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]] 2.8&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ACE:ACETYL+GROUP'>ACE</scene>, <scene name='pdbligand=B3D:3-AMINOPENTANEDIOIC+ACID'>B3D</scene>, <scene name='pdbligand=B3E:(3S)-3-AMINOHEXANEDIOIC+ACID'>B3E</scene>, <scene name='pdbligand=B3L:(3S)-3-AMINO-5-METHYLHEXANOIC+ACID'>B3L</scene>, <scene name='pdbligand=BAL:BETA-ALANINE'>BAL</scene>, <scene name='pdbligand=HMR:BETA-HOMOARGININE'>HMR</scene>, <scene name='pdbligand=XCP:(1S,2S)-2-AMINOCYCLOPENTANECARBOXYLIC+ACID'>XCP</scene>, <scene name='pdbligand=XPC:(3S,4R)-4-AMINOPYRROLIDINE-3-CARBOXYLIC+ACID'>XPC</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=3hex FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3hex OCA], [https://pdbe.org/3hex PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=3hex RCSB], [https://www.ebi.ac.uk/pdbsum/3hex PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=3hex ProSAT]</span></td></tr>
</table>
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== Publication Abstract from PubMed ==
We report high-resolution crystal structures of six new alpha/beta-peptide foldamers that have a regular alpha-residue/alpha-residue/beta-residue (alphaalphabeta) backbone repeat pattern. All of these foldamers were crystallized from aqueous solution, and all display four-helix bundle quaternary structure in the crystalline state. These oligomers are based on the well-studied 33-residue alpha-peptide GCN4-pLI, which is an engineered derivative of the dimerization domain of GCN4, a yeast transcription factor. GCN4-pLI forms a stable tetramer in solution and crystallizes as a four-helix bundle (Harbury et al. Science 1993, 262, 1401-1407). Previously we described a foldamer (designated 1 here) that was generated from GCN4-pLI by replacing every third alpha-amino acid residue with the homologous beta(3)-amino acid residue; this alphaalphabeta oligomer retains the side chain sequence of the original alpha-peptide, but the backbone contains 11 additional CH(2) units, which are evenly distributed (Horne et al. Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 9151-9156). Despite the expanded backbone, 1 was found to retain the ability to form a tetrameric quaternary structure in which the individual molecules adopt an alpha-helix-like conformation. Here we compare nine analogues of 1 that have the same alphaalphabeta backbone but in which one or more of the flexible beta(3)-amino acid residues is/are replaced with an analogous cyclic beta-residue. The motivation for beta(3)--&gt;cyclic replacements is to enhance conformational stability; however, a crystal structure of the one previously reported example (designated 2 here) revealed a "stammer" distortion of the helix-bundle architecture relative to 1. The results reported here suggest that the stammer is a peculiarity of 2, because all six of the new alpha/beta-peptides display undistorted four-helix bundle quaternary structures. More broadly, our results indicate that beta(3)--&gt;cyclic replacements are generally well-accommodated in helix-bundle quaternary structure, but that such replacements can be destabilizing in certain instances.

Structural consequences of beta-amino acid preorganization in a self-assembling alpha/beta-peptide: fundamental studies of foldameric helix bundles.,Price JL, Horne WS, Gellman SH J Am Chem Soc. 2010 Sep 8;132(35):12378-87. PMID:20718422<ref>PMID:20718422</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 3hex" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Large Structures]]
[[Category: Gellman SH]]
[[Category: Horne WS]]
[[Category: Price JL]]