PROSITE documentation PDOC50176

Armadillo/plakoglobin ARM repeat profile

The armadillo repeat is an approximately 40 amino acids long tandemly repeated sequence motif first identified in the Drosophila segment polarity gene product armadillo, a protein that mediates cell adhesion. Similar repeats were later found in the mammalian armadillo homolog β-catenin, the junctional plaque protein plakoglobin, the adenomatous polyposis coli (APC) tumor suppressor protein, and a number of other proteins [1]. These proteins exert several functions through interactions of their tandem armadillo repeats domain with diverse binding partners. The proteins combine structural roles as cell-contact and cytoskeleton-associated proteins and signaling functions by generating and transducing signals affecting gene expression [1,2,3].

The three-dimensional fold of an armadillo repeat is known from the crystal structure of β-catenin [4]. There, the 12 repeats form a superhelix of α-helices, with three helices per unit. The cylindrical structure features a positively charged grove which presumably interacts with the acidic surfaces of the known interaction partners of β-catenin.