Foldit Wiki

The Kelch domain-containing protein in the KLHDC2 puzzles has six "blades", each one an example of a Kelch motif. The blades form a "beta-propeller". The protein in this image is PDB 6DO5, shown in Jmol with the amino acid coloring scheme.

The term Kelch is implicitly referenced by the KLHDC2 ligand design puzzles. "KLHDC2" is shorthand for "Kelch domain-containing protein 2".

Kelch is considered a "motif", a section of a protein which appears in many places, with slight variations in each spot. As described in the wikipedia article Kelch motif, Kelch is composed of about 50 amino acid residues which form a structure of a four stranded beta-sheet "blade". Multiple instances of the Kelch motif in turn combine to form a "beta-propeller".

In the KLHDC2 puzzles in Foldit, only small fragments of the Kelch protein appear. The full structure can be seen in PDB entries 6DO3, 6DO4, and 6DO5.

According to the wikipedia article Kelch protein, the word "Kelch" is German for "cup" or "chalice". A certain mutation to a Kelch protein in fruit flies causes them to lay cup-shaped eggs, which led to the identification of the first Kelch protein.