SOLUTION STRUCTURE OF CDC42 IN COMPLEX WITH THE GTPASE BINDING DOMAIN OF WASP
[WASP_HUMAN] Defects in WAS are the cause of Wiskott-Aldrich syndrome (WAS) [MIM:301000]; also known as eczema-thrombocytopenia-immunodeficiency syndrome. WAS is an X-linked recessive immunodeficiency characterized by eczema, thrombocytopenia, recurrent infections, and bloody diarrhea. Death usually occurs before age 10.           Defects in WAS are the cause of thrombocytopenia type 1 (THC1) [MIM:313900]. Thrombocytopenia is defined by a decrease in the number of platelets in circulating blood, resulting in the potential for increased bleeding and decreased ability for clotting.     Defects in WAS are a cause of neutropenia severe congenital X-linked (XLN) [MIM:300299]. XLN is an immunodeficiency syndrome characterized by recurrent major bacterial infections, severe congenital neutropenia, and monocytopenia.
[CDC42_HUMAN] Plasma membrane-associated small GTPase which cycles between an active GTP-bound and an inactive GDP-bound state. In active state binds to a variety of effector proteins to regulate cellular responses. Involved in epithelial cell polarization processes. Regulates the bipolar attachment of spindle microtubules to kinetochores before chromosome congression in metaphase. Plays a role in the extension and maintenance of the formation of thin, actin-rich surface projections called filopodia. Mediates CDC42-dependent cell migration.   [WASP_HUMAN] Effector protein for Rho-type GTPases. Regulates actin filament reorganization via its interaction with the Arp2/3 complex. Important for efficient actin polymerization. Possible regulator of lymphocyte and platelet function. Mediates actin filament reorganization and the formation of actin pedestals upon infection by pathogenic bacteria.  
Publication Abstract from PubMed
The Rho-family GTP-hydrolysing proteins (GTPases), Cdc42, Rac and Rho, act as molecular switches in signalling pathways that regulate cytoskeletal architecture, gene expression and progression of the cell cycle. Cdc42 and Rac transmit many signals through GTP-dependent binding to effector proteins containing a Cdc42/Rac-interactive-binding (CRIB) motif. One such effector, the Wiskott-Aldrich syndrome protein (WASP), is postulated to link activation of Cdc42 directly to the rearrangement of actin. Human mutations in WASP cause severe defects in haematopoletic cell function, leading to clinical symptoms of thrombocytopenia, immunodeficiency and eczema. Here we report the solution structure of a complex between activated Cdc42 and a minimal GTPase-binding domain (GBD) from WASP. An extended amino-terminal GBD peptide that includes the CRIB motif contacts the switch I, beta2 and alpha5 regions of Cdc42. A carboxy-terminal beta-hairpin and alpha-helix pack against switch II. The Phe-X-His-X2-His portion of the CRIB motif and the alpha-helix appear to mediate sensitivity to the nucleotide switch through contacts to residues 36-40 of Cdc42. Discrimination between the Rho-family members is likely to be governed by GBD contacts to the switch I and alpha5 regions of the GTPases. Structural and biochemical data suggest that GBD-sequence divergence outside the CRIB motif may reflect additional regulatory interactions with functional domains that are specific to individual effectors.
Structure of Cdc42 in complex with the GTPase-binding domain of the 'Wiskott-Aldrich syndrome' protein.,Abdul-Manan N, Aghazadeh B, Liu GA, Majumdar A, Ouerfelli O, Siminovitch KA, Rosen MK Nature. 1999 May 27;399(6734):379-83. PMID:10360578
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.