Symbol Arm Pfam clan CL0020 SMART SM00185 | Pfam PF00514 InterPro IPR000225 PROSITE PS50176 | |
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An armadillo repeat is the name of a characteristic, repetitive amino acid sequence of about 40 residues in length that is found in many proteins. Proteins that contain armadillo repeats typically contain several tandemly repeated copies. Each Armadillo repeat is composed of a pair of alpha helices that form a hairpin structure. Multiple copies of the repeat form what is known as an alpha solenoid structure.
Examples of proteins that contain armadillo repeats include β-catenin, 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. β-catenin is a protein involved in linking cadherin cell adhesion proteins to the cytoskeleton, 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 beta-catenin, where the 12 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 beta-catenin.