Cysteine Modifiers Suggest an Allosteric Inhibitory Site on the CAL PDZ Domain

Yu Zhao, Patrick R Cushing, David C Smithson, Maria Pellegrini, Alexandre A Pletnev, Sahar Al-Ayyoubi, Andrew V Grassetti, Scott A Gerber, R Kiplin Guy, Dean R Madden

Biosci Rep. 2018 Jul 6;38(4):BSR20180231.

PMID: 29472314

Abstract:

Protein-protein interactions have become attractive targets for both experimental and therapeutic interventions. The PSD-95/Dlg1/ZO-1 (PDZ) domain is found in a large family of eukaryotic scaffold proteins that plays important roles in intracellular trafficking and localization of many target proteins. Here, we seek inhibitors of the PDZ protein that facilitates post-endocytic degradation of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR): the CFTR-associated ligand (CAL). We develop and validate biochemical screens and identify methyl-3,4-dephostatin (MD) and its analog ethyl-3,4-dephostatin (ED) as CAL PDZ inhibitors. Depending on conditions, MD can bind either covalently or non-covalently. Crystallographic and NMR data confirm that MD attacks a pocket at a site distinct from the canonical peptide-binding groove, and suggests an allosteric connection between target residue Cys319 and the conserved Leu291 in the GLGI motif. MD and ED thus appear to represent the first examples of small-molecule allosteric regulation of PDZ:peptide affinity. Their mechanism of action may exploit the known conformational plasticity of the PDZ domains and suggests that allosteric modulation may represent a strategy for targeting of this family of protein-protein binding modules.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
IAR4243158	Ethyl-3,4-dephostatin			Price
IAR4244037	Methyl-3,4-dephostatin			Price