Structure of the PCET/KIX complex. (A) Overlay of the 20 low-energy structures of the complex, with the backbone (N, Cα, C′ atoms) of residues Lys15-Ser28 of HEB-PCET (orange) and residues 589-685 of KIX (teal) displayed. (B) Ribbon diagram of the energy-minimized average structure of the HEB-PCET/KIX complex. The helices of KIX are labeled H1, H2, and H3, and the N- and C-termini are indicated. (C) Transparent surface of KIX displaying the backbone ribbon and the residues involved in intermolecular van der Waals contacts. (D) Ribbon representation of HEB-PCET (in orange) showing the position of residues Glu16, Leu17, Leu20, and Leu21 on the surface of KIX. (E) Ribbon representation of HEB-PCET (in orange) showing the position of the LDFS sequence (Leu21, Asp22, Phe23, and Ser24) as well as Ala25 and Phe27 on the surface of KIX. Residues are numbered by position in full-length CBP or HEB.