kelch proteins (and kelch-like proteins) are a widespread group of proteins that contain multiple kelch motifs. the kelch domain generally occurs as a set of five to seven kelch tandem repeats that form a β-propeller tertiary structure. kelch-repeat β-propellers are generally involved in protein–protein interactions, though the large diversity of domain architectures and limited sequence identity between kelch motifs make characterisation of the kelch superfamily difficult.