Kelch repeat - Kelch

Kelch is a 50-residue motif, named after the Drosophila mutant in which it was first identified. This sequence motif represents one beta-sheet blade, and several of these repeats can associate to form a beta-propeller. For instance, the motif appears 6 times in Drosophila egg-chamber regulatory protein, creating a 6-bladed beta-propeller. The motif is also found in mouse protein MIPP and in a number of poxviruses. The structure of galactose oxidase reveals that the repeated sequence corresponds to a 4-stranded anti-parallel beta-sheet motif that forms the repeat unit in a super-barrel structural fold. The known functions of kelch-containing proteins are diverse: scruin is an actin cross-linking protein; galactose oxidase catalyses the oxidation of the hydroxyl group at the C6 position in D-galactose; neuraminidase hydrolyses sialic acid residues from glycoproteins; and kelch may have a cytoskeletal function.