1m3w
From Proteopedia
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Crystal Structure of a Molecular Maquette Scaffold
Overview
Maquettes are de novo designed mimicries of nature used to test the, construction and engineering criteria of oxidoreductases. One type of, scaffold used in maquette construction is a four-alpha-helical bundle. The, sequence of the four-alpha-helix bundle maquettes follows a heptad repeat, pattern typical of left-handed coiled-coils. Initial designs were molten, globular due partly to the minimalist approach taken by the designers., Subsequent iterative redesign generated several structured scaffolds with, similar heme binding properties. Variant [I(6)F(13)](2), a structured, scaffold, was partially resolved with NMR spectroscopy and found to have a, set of mobile inter-helical packing interfaces. Here, the X-ray structure, of a similar peptide ([I(6)F(13)M(31)](2) i.e. ([CGGG EIWKL HEEFLKK, FEELLKL HEERLKKM](2))(2) which we call L31M), has been solved using MAD, phasing and refined to 2.8A resolution. The structure shows that the, maquette scaffold is an anti-parallel four-helix bundle with, "up-up-down-down" topology. No pre-formed heme-binding pocket exists in, the protein scaffold. We report unexpected inter-helical crossing angles, residue positions and translations between the helices. The crossing, angles between the parallel helices are -5 degrees rather than the, expected +20 degrees for typical left-handed coiled-coils. Deviation of, the scaffold from the design is likely due to the distribution and size of, hydrophobic residues. The structure of L31M points out that four identical, helices may interact differently in a bundle and heptad repeats with an, alternating [HPPHHPP]/[HPPHHPH] (H: hydrophobic, P: polar) pattern are not, a sufficient design criterion to generate left-hand coiled-coils.
About this Structure
1M3W is a Protein complex structure of sequences from [1] with HG and NH2 as ligands. Full crystallographic information is available from OCA.
Reference
X-ray structure of a maquette scaffold., Huang SS, Gibney BR, Stayrook SE, Leslie Dutton P, Lewis M, J Mol Biol. 2003 Feb 28;326(4):1219-25. PMID:12589764
Page seeded by OCA on Sun Nov 25 03:43:54 2007
