Binding of Crumbs to the Par-6 CRIB-PDZ Module Is Regulated by Cdc42

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• 作者：Dustin S. Whitney ; Francis C. Peterson ; Aaron W. Kittell ; John M. Egner ; Kenneth E. Prehoda ; Brian F. Volkman
• 刊名：Biochemistry
• 出版年：2016
• 出版时间：March 15, 2016
• 年：2016
• 卷：55
• 期：10
• 页码：1455-1461
• 全文大小：387K
• ISSN：1520-4995

文摘

Par-6 is a scaffold protein that organizes other proteins into a complex required to initiate and maintain cell polarity. Cdc42-GTP binds the CRIB module of Par-6 and alters the binding affinity of the adjoining PDZ domain. Allosteric regulation of the Par-6 PDZ domain was first demonstrated using a peptide identified in a screen of typical carboxyl-terminal ligands. Crumbs, a membrane protein that localizes a conserved polarity complex, was subsequently identified as a functional partner for Par-6 that likely interacts with the PDZ domain. Here we show by nuclear magnetic resonance that Par-6 binds a Crumbs carboxyl-terminal peptide and report the crystal structure of the PDZ–peptide complex. The Crumbs peptide binds Par-6 more tightly than the previously studied carboxyl peptide ligand and interacts with the CRIB-PDZ module in a Cdc42-dependent manner. The Crumbs:Par-6 crystal structure reveals specific PDZ–peptide contacts that contribute to its higher affinity and Cdc42-enhanced binding. Comparisons with existing structures suggest that multiple C-terminal Par-6 ligands respond to a common conformational switch that transmits the allosteric effects of GTPase binding.