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Figure 2
Crystal structure of PDZ tandem (181-PA14-184) complexed with the NZ-1 Fab. (a, b) Crystal packing in two different views. The crystallographic axes are indicated with arrows. The complex is shown as a surface model and the neighboring complexes in the crystal lattice are shown with partial transparency. The heavy chain and light chain of the Fab are colored dark and light orange, respectively. The PDZ-N and PDZ-C domains are colored green and cyan, respectively; the inserted PA14 tag is colored magenta. (c) Overall structure of the complex. The NZ-1 Fab docks to PDZ-N through PA14 and does not make direct contacts with PDZ-C within the complex. (d) Superposition of the Cα traces. The wild-type PDZ-N domain and the PA12- and PA14-inserted mutants are colored as in (c) and shown in light, medium and dark colors, respectively. The structures of the wild-type and PA12-inserted PDZ-N domains were extracted from previously determined crystal structures [PDB entries 3wkl (wild type) and 6al1 (PA12-inserted mutant)]. The turn residues replaced by the insertion (Asn182 and Gly183) and the inserted sequences (PA12 and PA14) are colored magenta, except for Glu1′ and Gly2′ in PA14, which are colored blue. In the PA12-inserted mutant, the junction residues highlighted in yellow (Glu184–His187) alter their conformations on PA12 insertion and complex formation. In contrast, the addition of Glu1′ and Gly2′ seemed to induce less structural change of the target PDZ-N domain, including the junction residues, in the PA14-inserted mutant. (e) Close-up view of the binding site. The NZ-1 Fab is shown as in (c). The PDZ-N domain and the inserted PA14 are shown as stick models and colored as in (d). Arg181 and Glu184 in the PDZ-N domain maintained the inter-strand hydrogen bond, as shown by dotted lines. (f) Residues at the binding interface. The binding interface from (e) is shown as a ribbon model and in profile. Residues where the side chains are presumed to form salt bridges or hydrogen bonds are displayed as stick models.

Journal logoSTRUCTURAL
ISSN: 2059-7983
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