Abstract

Wiskott-Aldrich syndrome protein (WASP) and WIP (WASP interacting protein)form a complex that has a pivotal function in integrating sigalling cascades that lead to acting polymerization.

The WASP binding domain (WBD) in WIP is known to bind to the WH1 (WASP homology 1) domain of WASP and N-WASP. The strong sequence conservation between the WH1 and the EVH1 domains, including the residues involved in coordinating EVH1 binding to FPPPP ligands, suggested that the WH1 domain may also bind a prolin-rich ligand. Indeed, the WBD in WIP consists of 26% proline residues and contains four proline sequence motifs, one of which is closely related to the VASP EVH1 binding motif.However it was found that WH1 and EVH1 domains bind distinct sequence motifs. The N-WASP WH1 binding motif of WIP is highly conserved also in the mammalian WIP homologs CR16 and WICH, two proteins interacting with N-WASP.