This is a WW domain found in histone-lysine N-methyltransferase, H3 lysine-36 specific (EC:2.1.1.43) in Saccharomyces cerevisiae. The WW domain is the simplest natural beta-sheet structure. It is a 35-residue protein module found in signaling and regulatory proteins with two highly conserved tryptophans and a strictly conserved proline.

1: Structural analysis of WW domains and design of a WW prototype. Macias MJ, Gervais V, Civera C, Oschkinat H; Nat Struct Biol. 2000;7:375-379. PMID:10802733