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Figure 4
Comparison of the two conformations of PDZ tandem (235-PA14-236) complexed with the NZ-1 Fab. (a, b) Comparison of crystal contacts in complexes 1 and 2 with PA14-inserted PDZ-C domains. The structures are shown as in Figs. 3[link](a) and 3[link](b). In both complexes 1 and 2, the PDZ-C domains were in direct contact with two neighboring complexes, labeled neighbor-1 and neighbor-2. The PDZ-C domain of complex 1 had a relatively small contact area with neighbor-2 where solvent-accessible space was present between them. The relative arrangement of the NZ-1 Fab and PDZ-C in complex 1 did not appear to be affected by the crystal packing. In contrast, the PDZ-C domain of complex 2 intimately interacted with neighbor-2, indicating that the positioning of the PDZ-C domain with respect to the NZ-1 Fab was restricted by the crystal packing. (c) Superposition of the Cα traces. The wild-type PDZ-C domain (PDB entry 3wkl) and the PA14-inserted mutants in complexes 1 and 2 are shown in dark, medium and light colors, respectively. The PDZ-C domain is shown in cyan, while the insertion site (Asn235 and Gly236) is colored orange. The inserted PA14 tags are colored as in Figs. 3[link](c) and 3[link](d). (d) Superposition of the two complexes based on the NZ-1 Fab. The NZ-1 Fab in complex 1 is shown as a surface model. The heavy chain and light chains are colored gray and white, respectively. The interaction modes of Gly3′ and Val4′ of PA14 shown in yellow were different between the two complexes. As a result, the superposition showed a rigid-body rotational movement of the PDZ-C domain around the PA14-insertion site. (e, f) Residues at the binding interfaces of complexes 1 (e) and 2 (f). Residues presumed to form salt bridges or hydrogen bonds are displayed as stick models in the ribbon models.

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ISSN: 2059-7983
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