Phosphorylation of a PDZ Domain Extension Modulates Binding Affinity and Interdomain Interactions in Postsynaptic Density-95 (PSD-95) Protein, a Membrane-associated Guanylate Kinase (MAGUK)

• Published in: The Journal of biological chemistry 2011-12, Vol.286 (48), p.41776-41785
• Main Authors: Zhang, Jun, Petit, Chad M., King, David S., Lee, Andrew L.
• Format: Article
• Language: English
• Subjects: Allosteric Regulation; Allosteric Regulation - physiology; Biophysics; Disks Large Homolog 4 Protein; Guanylate Kinases - chemistry; Guanylate Kinases - genetics; Guanylate Kinases - metabolism; Humans; Intracellular Signaling Peptides and Proteins - chemistry; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - metabolism; MAGUK; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; NMR Dynamics; Nuclear Magnetic Resonance; Nuclear Magnetic Resonance, Biomolecular; PDZ Domains; PDZ3; Phosphorylation; Phosphorylation - physiology; Protein Dynamics; Protein Structure and Folding; PSD-95; src Homology Domains; Structure-Activity Relationship
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.272583

Postsynaptic density-95 is a multidomain scaffolding protein that recruits glutamate receptors to postsynaptic sites and facilitates signal processing and connection to the cytoskeleton. It is the leading member of the membrane-associated guanylate kinase family of proteins, which are defined by the PSD-95/Discs large/ZO-1 (PDZ)-Src homology 3 (SH3)-guanylate kinase domain sequence. We used NMR to show that phosphorylation of conserved tyrosine 397, which occurs in vivo and is located in an atypical helical extension (α3), initiates a rapid equilibrium of docked and undocked conformations. Undocking reduced ligand binding affinity allosterically and weakened the interaction of PDZ3 with SH3 even though these domains are separated by a ∼25-residue linker. Additional phosphorylation at two linker sites further disrupted the interaction, implicating α3 and the linker in tuning interdomain communication. These experiments revealed a novel mode of regulation by a detachable PDZ element and offer a first glimpse at the dynamic interaction of PDZ and SH3-guanylate kinase domains in membrane-associated guanylate kinases.