Deciphering the unconventional peptide binding to the PDZ domain of MAST2

Phosphatase and tensin homologue (PTEN) and microtubule-associated serine threonine kinase 2 (MAST2) are key negative regulators of survival pathways in neuronal cells. The two proteins interact via the PDZ (PSD-95, Dlg1, Zo-1) domain of MAST2 (MAST2–PDZ). During infection by rabies virus, the viral glycoprotein competes with PTEN for interaction with MAST2–PDZ and promotes neuronal survival. The C-terminal PDZ-binding motifs (PBMs) of the two proteins bind similarly to MAST2–PDZ through an unconventional network of connectivity involving two anchor points. Combining stopped-flow fluorescence, analytical ultracentrifugation (AUC), microcalorimetry and NMR, we document the kinetics of interaction between endogenous and viral ligands to MAST2–PDZ as well as the dynamic and structural effects of these interactions. Viral and PTEN peptide interactions to MAST2–PDZ occur via a unique kinetic step which involves both canonical C-terminal PBM binding and N-terminal anchoring. Indirect effects induced by the PBM binding include modifications to the structure and dynamics of the PDZ dimerization surface which prevent MAST2–PDZ auto-association. Such an energetic communication between binding sites and distal surfaces in PDZ domains provides interesting clues for protein regulation overall.