2ipz
From Proteopedia
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A Parallel Coiled-Coil Tetramer with Offset Helices
Overview
Specific helix-helix interactions are fundamental in assembling the native, state of proteins and in protein-protein interfaces. Coiled coils afford a, unique model system for elucidating principles of molecular recognition, between alpha helices. The coiled-coil fold is specified by a, characteristic seven amino acid repeat containing hydrophobic residues at, the first (a) and fourth (d) positions. Nonpolar side chains spaced three, and four residues apart are referred to as the 3-4 hydrophobic repeat. The, presence of apolar amino acids at the e or g positions (corresponding to a, 3-3-1 hydrophobic repeat) can provide new possibilities for close-packing, of alpha-helices that includes examples such as the lac repressor, tetramerization domain. Here we demonstrate that an unprecedented, coiled-coil interface results from replacement of three charged residues, at the e positions in the dimeric GCN4 leucine zipper by nonpolar valine, side chains. Equilibrium circular dichroism and analytical, ultracentrifugation studies indicate that the valine-containing mutant, forms a discrete alpha-helical tetramer with a significantly higher, stability than the parent leucine-zipper molecule. The 1.35 A resolution, crystal structure of the tetramer reveals a parallel four-stranded coiled, coil with a three-residue interhelical offset. The local packing geometry, of the three hydrophobic positions in the tetramer conformation is, completely different from that seen in classical tetrameric structures yet, bears resemblance to that in three-stranded coiled coils. These studies, demonstrate that distinct van der Waals interactions beyond the a and d, side chains can generate a diverse set of helix-helix interfaces and, three-dimensional supercoil structures.
About this Structure
2IPZ is a Single protein structure of sequence from Saccharomyces cerevisiae with GOL and IPA as ligands. Full crystallographic information is available from OCA.
Reference
A parallel coiled-coil tetramer with offset helices(,)., Liu J, Deng Y, Zheng Q, Cheng CS, Kallenbach NR, Lu M, Biochemistry. 2006 Dec 26;45(51):15224-31. Epub 2006 Nov 29. PMID:17176044
Page seeded by OCA on Wed Nov 21 12:25:08 2007
