This short conserved region is a putative destruction-box, with its RxxLxxI sequence motif, though the homology is not absolute [3]. The domain occurs on a number of tumourigenic proteins, on some RNA-binding proteins and serine-threonine regulatory proteins [1]. The second less well-conserved motif, WITPS, is a potential WW domain ligand-binding motif for recruiting proteins to their substrates. WW domains bind tightly to short proline-containing peptides that are typically in regions of native disordered polypeptide, as this family is as it lies between a PIN domain and a zinc-binding domain [2].

1: Cloning, expression and characterization of the human NOB1 gene. Zhang Y, Ni J, Zhou G, Yuan J, Ren W, Shan Y, Tang W, Yu L, Zhao S; Mol Biol Rep. 2005;32:185-189. PMID:16172919

2: Function of WW domains as phosphoserine- or phosphothreonine-binding modules. Lu PJ, Zhou XZ, Shen M, Lu KP; Science 1999;283:1325-1328. PMID:10037602

3: Control of the SCF(Skp2-Cks1) ubiquitin ligase by the APC/C(Cdh1) ubiquitin ligase. Bashir T, Dorrello NV, Amador V, Guardavaccaro D, Pagano M; Nature. 2004;428:190-193. PMID:15014502