WW domain of Pin1 bound to a doubly phosphorylated peptide.
WW domains are small, 38 to 40 amino acid residue modules implicated in binding to Pro-rich sequences. WW domains and SH3 domains can potentially bind overlapping sites. In addition, the Pin1 WW domain functions as a phosphoserine or phosphothreonine binding module, suggesting that certain WW domains have evolved an alternate mode of action. WW domains bind peptide ligands with dissociation constants in the µM range.
| WW Domain Proteins | Binding Partners | WW Domain Binding Sites |
| Yes-Associated Protein (YAP) | Yes, Src-like Tyrosine Kinase | PPPPY |
| Nedd4 E3 Ubiquitin Ligase | ΒENaC amiloride-E3 ubiquitin ligase-sensitive epithelial Na+ channel | PPPNY |
| FBP – 11 | Formin | PPLP |
