Structures of the human Pals1 PDZ domain with and without ligand suggest gated access of Crb to the PDZ peptide-binding groove

Ivanova, M.E.; Fletcher, G.C.; O'Reilly, N.; Purkiss, A.G.; Thompson, B.J.; McDonald, N.Q.

doi:10.1107/S139900471402776X

Figure 4
Crb¹⁷ recognition by Pals1^PDZ and Par6^PDZ and the similarity of ligand-free Pals1^PDZ to Par6^PDZ bound to an internal peptide ligand. (a) Sequence alignment of the human Pals1 and Par6 PDZ domains. Residue numbering for Par6 and Pals1 is shown above and below the alignment; secondary structure for Pals1 is shown below the alignment (arrows represent β-strands and helices represent α-helices); the carboxylate-binding loop is highlighted by a red box and residues making contacts with the Crb¹⁷ peptide are highlighted in red. (b) Surface conservation of Pals1/Par6 close to the ERLI ligand is shown in deep blue (identical), light blue (similar) and white (not conserved). The Crb¹⁷ peptide is shown in purple with the ERLI motif side chains, except for Arg1404, all making conserved contacts. This is consistent with the known Par6 PDZ-binding ligands ESLV (PDB entry 1rzx ) and EMAV (PDB entry 1x8s ), varying at the second position (equivalent to Arg1404 of Crb). (c) Superimposition of Par6^PDZ bound to the Pals1 internal ligand (light blue; PDB entry 1x8s ), the ligand-free form of Pals1^PDZ (light pink), Par6^PDZ bound to the C-terminal ligand (dark blue; PDB entry 1rzx ) and Pals1^PDZ bound to the C-terminal Crb¹⁷ ligand (purple). The carboxylate-binding loop in each structure is highlighted according to the colour legend in the figure.

BIOLOGICAL
CRYSTALLOGRAPHY

ISSN: 1399-0047

Volume 71| Part 3| February 2015| Pages 555-564

doi:10.1107/S139900471402776X

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