ERCC2 and trichothiodystrophy: The importance of this conserved arginine/lysine residue in FeS cluster coordination is further underlined by the fact that the homologous residue in human XPD (arginine-112) is required for helicase activity (Dubaele et al, 2003; Rudolf et al, 2006) and affected in the XPD-linked disorder trichothiodystrophy (Botta et al, 2002).