FAAP20 and Friedreich ataxia: FANCA is the largest protein in the complex, and mutation in FANCA accounts for more than 65% of FA patients in the U.S.A. and Europe [16]; FANCG contains multiple tetratricopeptide repeat motifs (TPRs) that act as scaffolds in multiprotein complexes [49] and FAAP20 is a small protein made up almost entirely of a UBZ-like ubiquitin binding domain [50].