Fig. 4. Structure of -catenin complexes in the -catenin destruction complex. Crystal structures of the -catenin armadillo repeat domain in complex with the phosphorylated third 20aa repeat of APC (in red) and the -catenin-binding domain of axin (in blue) were superimposed on the structure of the -catenin armadillo repeat domain. The positions of the four phosphorylated residues in APC 20aa repeat 3 are shown.