title: 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).
abstract: 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.
authors.affiliation: Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599.
authors.forename: Chad M
authors.initials: CM
authors.lastname: Petit
authors.affiliation: Howard Hughes Medical Institute Mass Spectrometry Laboratory and Department of Molecular and Cell Biology, University of California, Berkeley, California 94720.
authors.forename: David S
authors.initials: DS
authors.lastname: King
authors.affiliation: Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599; Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599. Electronic address: drewlee@unc.edu.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Lee
mesh_terms: D000494:Allosteric Regulation / Q000502:physiology; D000076122:Disks Large Homolog 4 Protein; D051528:Guanylate Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D054731:PDZ Domains; D010766:Phosphorylation / Q000502:physiology; D013329:Structure-Activity Relationship; D018909:src Homology Domains
chemical_list: C501444:DLG4 protein, human; D000076122:Disks Large Homolog 4 Protein; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051528:Guanylate Kinases