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Mol Cell. 2004 Mar 12;13(5):665-76.

Cdc42 regulates the Par-6 PDZ domain through an allosteric CRIB-PDZ transition.

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1
Department of Biochemistry, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226 USA.

Abstract

Regulation of protein interaction domains is required for cellular signaling dynamics. Here, we show that the PDZ protein interaction domain from the cell polarity protein Par-6 is regulated by the Rho GTPase Cdc42. Cdc42 binds to a CRIB domain adjacent to the PDZ domain, increasing the affinity of the Par-6 PDZ for its carboxy-terminal ligand by approximately 13-fold. Par-6 PDZ regulation is required for function as mutational disruption of Cdc42-Par-6 PDZ coupling leads to inactivation of Par-6 in polarized MDCK epithelial cells. Structural analysis reveals that the free PDZ domain has several deviations from the canonical PDZ conformation that account for its low ligand affinity. Regulation results from a Cdc42-induced conformational transition in the CRIB-PDZ module that causes the PDZ to assume a canonical, high-affinity PDZ conformation. The coupled CRIB and PDZ architecture of Par-6 reveals how simple binding domains can be combined to yield complex regulation.

PMID:
15023337
[Indexed for MEDLINE]
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