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From Wikipedia, the free encyclopedia
An armadillo repeat is a characteristic, repetitive amino acid sequence of about 42 residues in length that is found in many proteins. Proteins that contain armadillo repeats typically contain several tandemly repeated copies.[2][3] 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, Sarm1 (SARM1),[4] α-importin,[5] plakoglobin,[6] adenomatous polyposis coli (APC),[7] 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.[8] 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.
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.[1] The cylindrical structure features a positively charged groove, which presumably interacts with the acidic surfaces of the known interaction partners of β-catenin.[9]
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