This puzzle introduces a new secondary structure, the poly-proline helix! The starting structure is a small 38 residue protein with a frozen helix and designable residues on either end. Players should fold the starting structure to create a compact globular protein that incorporates this new type of secondary structure. Note that the backbone of the poly-proline helix has bondable oxygen atoms. If any of these oxygens are buried in the protein core, they will need to make hydrogen bonds! See the blog for more information!
If we are designing collagen-like structures, don't we need hydroxyproline as an amino acid?
see wikipedia
and
Gorres, Kelly L.; Raines, Ronald T. (April 2010). "Prolyl 4-hydroxylase". Critical Reviews in Biochemistry and Molecular Biology. 45 (2): 106–124.
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Collagen happens to contain hydroxyproline (a non-canonical amino acid), but poly-proline helices (and proteins that incorporate them) do not need to contain this residue. Currently Foldit works best with the 20 encoded amino acids, so we try to design puzzles with only these residues.