WW Domains

**Definition:** An approximately 40 amino acid protein domain that occurs in a variety of unrelated proteins and may be repeated up to four times in some proteins. It is characterized by two TRYPTOPHAN residues (WW) about 20 amino acids apart and folds into a stable triple-stranded BETA-SHEET. It binds PROLINE-RICH PROTEIN DOMAINS and PHOSPHOSERINE or PHOSPHOTHREONINE-containing protein domains that occur in many signal-transducing and cytoskeletal proteins such as DYSTROPHIN.

**Tree numbers:** - G02.111.570.820.709.275.750.500.937

**Synonyms:** - WW Domain