ADF Protein Domain

The approximately 40 amino acid Armadillo (ARM) repeat was first identified in the Drosophila segment polarity gene product Armadillo (the homologue of mammalian β-catenin). It has since been identified in over 240 different proteins of diverse cellular function from yeast to man. The ARM domain is implicated in mediating protein-protein interactions, but no common features among the target proteins recognized by the ARM repeats have been identified. The ARM repeat has a common phylogenetic origin with the HEAT repeat. Both ARM and HEAT repeats contain a set of seven highly conserved hydrophobic residues and both mediate protein-protein interactions. Although structurally similar, the ARM repeat consists of three helices (H1, H2, and H3) whereas HEAT repeats consist of two helices (A and B). However, the strongly bent helix A of HEAT repeats corresponds to helices 1 and 2 of ARM repeats.