2guv
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(New page: 200px<br /><applet load="2guv" size="450" color="white" frame="true" align="right" spinBox="true" caption="2guv, resolution 1.40Å" /> '''Conformational Trans...)
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Revision as of 09:16, 21 November 2007
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Conformational Transition between Four- and Five-stranded Phenylalanine Zippers Determined by a Local Packing Interaction
Overview
Alpha-helical coiled coils play a crucial role in mediating specific, protein-protein interactions. However, the rules and mechanisms that, govern helix-helix association in coiled coils remain incompletely, understood. Here we have engineered a seven heptad "Phe-zipper" protein, (Phe-14) with phenylalanine residues at all 14 hydrophobic a and d, positions, and generated a further variant (Phe-14(M)) in which a single, core Phe residue is substituted with Met. Phe-14 forms a discrete, alpha-helical pentamer in aqueous solution, while Phe-14(M) folds into a, tetrameric helical structure. X-ray crystal structures reveal that in both, the tetramer and the pentamer the a and d side-chains interlock in a, classical knobs-into-holes packing to produce parallel coiled-coil, structures enclosing large tubular cavities. However, the presence of the, Met residue in the apolar interface of the tetramer markedly alters its, local coiled-coil conformation and superhelical geometry. Thus, short-range interactions involving the Met side-chain serve to, preferentially select for tetramer formation, either by inhibiting a, nucleation step essential for pentamer folding or by abrogating an, intermediate required to form the pentamer. Although specific trigger, sequences have not been clearly identified in dimeric coiled coils, higher-order coiled coils, as well as other oligomeric multi-protein, complexes, may require such sequences to nucleate and direct their, assembly.
About this Structure
2GUV is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Conformational transition between four and five-stranded phenylalanine zippers determined by a local packing interaction., Liu J, Zheng Q, Deng Y, Kallenbach NR, Lu M, J Mol Biol. 2006 Aug 4;361(1):168-79. Epub 2006 Jun 13. PMID:16828114
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