In this paper we show that N TAIL remains predominantly unfolded after binding to XD, with two distinct sites being involved in the interaction. Although the XDinduced gain of regular secondary is restricted to Box2 (aa 489-504), the region encompassing residues 489-504 is not the only N TAIL region involved in binding to XD. In particular, we present several lines of evidence indicating that the extreme C terminus of N TAIL (Box3, aa 517-525) also contributes to binding, without however gaining any regular secondary structure.