title: Solution structure and backbone dynamics of the second PDZ domain of postsynaptic density-95.
abstract: The second PDZ domain of postsynaptic density-95 (PSD-95 PDZ2) plays a critical role in coupling N-methyl-D-aspartate receptors to neuronal nitric oxide synthase (nNOS). In this work, the solution structure of PSD-95 PDZ2 was determined to high resolution by NMR spectroscopy. The structure of PSD-95 PDZ2 was compared in detail with that of alpha1-syntrophin PDZ domain, as the PDZ domains share similar target interaction properties. The interaction of the PSD-95 PDZ2 with a carboxyl-terminal peptide derived from a cytoplasmic protein CAPON was studied by NMR titration experiments. Complex formation between PSD-95 PDZ2 and the nNOS PDZ was modelled on the basis of the crystal structure of the alpha1-syntrophin PDZ/nNOS PDZ dimer. We found that the prolonged loop connecting the betaB and betaC strands of PSD-95 PDZ2 is likely to play a role in both the binding of the carboxyl-terminal peptide and the nNOS beta-finger. Finally, the backbone dynamics of the PSD-95 PDZ2 in the absence of bound peptide were studied using a model-free approach. The "GLGF"-loop and the loop connecting alphaB and betaF of the protein display some degree of flexibility in solution. The rest of the protein is rigid and lacks detectable slow time-scale (microseconds to milliseconds) motions. In particular, the loop connecting betaB and betaC loop adopts a well-defined, rigid structure in solution. It appears that the loop adopts a pre-aligned conformation for the PDZ domain to interact with its targets.
authors.affiliation: Department of Biochemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, Kowloon, P. R. China.
authors.forename: H
authors.initials: H
authors.lastname: Tochio
authors.forename: F
authors.initials: F
authors.lastname: Hung
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.forename: D S
authors.initials: DS
authors.lastname: Bredt
authors.forename: M
authors.initials: M
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D000076122:Disks Large Homolog 4 Protein; D047908:Intracellular Signaling Peptides and Proteins; D009682:Magnetic Resonance Spectroscopy; D008565:Membrane Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D011487:Protein Conformation; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D012996:Solutions
chemical_list: D017931:DNA Primers; D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011994:Recombinant Proteins; D012996:Solutions; C033652:postsynaptic density proteins