PMID: 19893486 , Related PDB ids: 3A8N, 3A8P, 3A8Q

Authors:

Terawaki S, Kitano K, Mori T, Zhai Y, Higuchi Y, Itoh N, Watanabe T, Kaibuchi K, Hakoshima T

Title:

The PHCCEx domain of Tiam1/2 is a novel protein- and membrane-binding module.

Journal:

EMBO J. 2010 Jan 6;29(1):236-50. Epub 2009 Nov 5.

Abstract:

Tiam1 and Tiam2 (Tiam1/2) are guanine nucleotide-exchange factors that possess the PH-CC-Ex (pleckstrin homology, coiled coil and extra) region that mediates binding to plasma membranes and signalling proteins in the activation of Rac GTPases. Crystal structures of the PH-CC-Ex regions revealed a single globular domain, PHCCEx domain, comprising a conventional PH subdomain associated with an antiparallel coiled coil of CC subdomain and a novel three-helical globular Ex subdomain. The PH subdomain resembles the beta-spectrin PH domain, suggesting non-canonical phosphatidylinositol binding. Mutational and binding studies indicated that CC and Ex subdomains form a positively charged surface for protein binding. We identified two unique acidic sequence motifs in Tiam1/2-interacting proteins for binding to PHCCEx domain, Motif-I in CD44 and ephrinB's and the NMDA receptor, and Motif-II in Par3 and JIP2. Our results suggest the molecular basis by which the Tiam1/2 PHCCEx domain facilitates dual binding to membranes and signalling proteins.