Armadillo repeat

Examples of proteins that contain armadillo repeats include β-catenin, Sarm1 (SARM1), α-importin, plakoglobin, adenomatous polyposis coli (APC), and many others.

The term armadillo derives from the historical name of the β-catenin gene in the fruitfly Drosophila where the armadillo repeat was first discovered. Although β-catenin was previously believed to be a protein involved in linking cadherin cell adhesion proteins to the cytoskeleton, recent work indicates that β-catenin regulates the homodimerization of alpha-catenin, which in turn controls actin branching and bundling. But, the armadillo repeat is found in a wide range of proteins with other functions. This type of protein domain is important in transducing WNT signals during embryonic development.

Structure

The 3-dimensional fold of an armadillo repeat was first observed in the crystal structure of β-catenin, where the 12 tandem repeats form a superhelix of alpha helices with three helices per unit. The cylindrical structure features a positively charged groove, which presumably interacts with the acidic surfaces of the known interaction partners of β-catenin.