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| [[Image:2gus.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_2gus| PDB=2gus | SCENE= }} | | {{STRUCTURE_2gus| PDB=2gus | SCENE= }} |
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| '''Conformational Transition between Four- and Five-stranded Phenylalanine Zippers Determined by a Local Packing Interaction'''
| | ===Conformational Transition between Four- and Five-stranded Phenylalanine Zippers Determined by a Local Packing Interaction=== |
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| ==Overview==
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| 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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_16828114}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 16828114 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_16828114}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Protein folding]] | | [[Category: Protein folding]] |
| [[Category: Tetramer]] | | [[Category: Tetramer]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 05:33:46 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 02:16:32 2008'' |
