Structural Determinants for High-Affinity Binding in a Nedd4 WW3 ∗ Domain-Comm PY Motif Complex

• Published in: Structure (London) Vol. 14; no. 3; pp. 543 - 553
• Main Authors: Kanelis, Voula, Bruce, M. Christine, Skrynnikov, Nikolai R., Rotin, Daniela, Forman-Kay, Julie D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.03.2006
• Subjects: Amino Acid Motifs; Amino Acid Sequence; Binding Sites; Drosophila Proteins - chemistry; Drosophila Proteins - genetics; Endosomal Sorting Complexes Required for Transport; Membrane Proteins - chemistry; Membrane Proteins - genetics; Molecular Sequence Data; MOLNEURO; Nedd4 Ubiquitin Protein Ligases; Peptides - chemistry; Protein Binding; Protein Folding; Protein Structure, Tertiary; SIGNALING; Solutions; Structure-Activity Relationship; Ubiquitin-Protein Ligases - chemistry; Ubiquitin-Protein Ligases - genetics; MOLNEURO; SIGNALING
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2005.11.018

Interactions between the WW domains of Drosophila Nedd4 (dNedd4) and Commissureless (Comm) PY motifs promote axon crossing at the CNS midline and muscle synaptogenesis. Here we report the solution structure of the dNedd4 WW3 ∗ domain complexed to the second PY motif ( 227′TG LPSYDEALH 237′) of Comm. Unexpectedly, there are interactions between WW3 ∗ and ligand residues both N- and C-terminal to the PY motif. Residues Y232′–L236′ form a helical turn, following the PPII helical PY motif. Mutagenesis and binding studies confirm the importance of these extensive contacts, not simultaneously observed in other WW domain complexes, and identify a variable loop in WW3 ∗ responsible for its high-affinity interaction. These studies expand our general understanding of the molecular determinants involved in WW domain-ligand recognition. In addition, they provide insights into the specific regulation of dNedd4-mediated ubiquitination of Comm and subsequent internalization of Comm or the Comm/Roundabout complex, critical for CNS and muscle development.