Binding coupled to folding has been reported for the phosphorylated kinase-inducible domain (pKID) of CREB, which undergoes a coil to a-helix folding transition upon binding to the KIX domain of the transcription coactivator CBP (CREB Binding Protein) (Radhakrishnan et al. 1997) . The amphipathic helix aB of pKID interacts with a hydrophobic groove defined by helices a1 and a3 of the partner. The other pKID helix, aA, contacts a different face of the a3 helix. This mode of interaction is reminiscent of that occurring between N TAIL and XD. Similarities concern the involvement of two distinct sites within the disordered domain (where Box2 and Box3 resemble helices aB and aA, respectively) and embedding of an a-helix within a hydrophobic cleft delimited by a-helices from the structured partner. The difference concerns the mode of interaction of the second site, where Box3 of N TAIL does not gain any regular secondary structure element, contrary to aA of pKID. Nevertheless, complexes with dual interaction have already been described in the literature. Among them, we mention the case of the binding of p27 to the cyclinA-Cdk2 complex (Lacy et al. 2004) , and that of the activation domain of CITED2 to the TAZ1 domain of CBP (De Guzman et al. 2004 ).