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| [[Image:2hy6.jpg|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_2hy6| PDB=2hy6 | SCENE= }} | | {{STRUCTURE_2hy6| PDB=2hy6 | SCENE= }} |
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| '''A seven-helix coiled coil'''
| | ===A seven-helix coiled coil=== |
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| ==Overview==
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| Coiled-coil proteins contain a characteristic seven-residue sequence repeat whose positions are designated a to g. The interacting surface between alpha-helices in a classical coiled coil is formed by interspersing nonpolar side chains at the a and d positions with hydrophilic residues at the flanking e and g positions. To explore how the chemical nature of these core amino acids dictates the overall coiled-coil architecture, we replaced all eight e and g residues in the GCN4 leucine zipper with nonpolar alanine side chains. Surprisingly, the alanine-containing mutant forms a stable alpha-helical heptamer in aqueous solution. The 1.25-A resolution crystal structure of the heptamer reveals a parallel seven-stranded coiled coil enclosing a large tubular channel with an unusual heptad register shift between adjacent staggered helices. The overall geometry comprises two interleaved hydrophobic helical screws of interacting cross-sectional a and d layers that have not been seen before. Moreover, asparagines at the a positions play an essential role in heptamer formation by participating in a set of buried interhelix hydrogen bonds. These results demonstrate that heptad repeats containing four hydrophobic positions can direct assembly of complex, higher-order coiled-coil structures with rich diversity for close packing of alpha-helices.
| | The line below this paragraph, {{ABSTRACT_PUBMED_17030805}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 17030805 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_17030805}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Protein design]] | | [[Category: Protein design]] |
| [[Category: Protein structure]] | | [[Category: Protein structure]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 06:51:29 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 06:26:30 2008'' |
