title: The second PDZ domain of INAD is a type I domain involved in binding to eye protein kinase C. Mutational analysis and naturally occurring variants.
abstract: INAD is a scaffolding protein containing five PSD95/dlg/zonular occludens-1 (PDZ) domains that tether NORPA (phospholipase Cbeta(4)), the TRP calcium channel, and eye-PKC in Drosophila photoreceptors. We previously showed that eye-PKC interacted with the second PDZ domain (PDZ2) of INAD. Sequence comparison with a prototypical type I PDZ domain predicts that PDZ2 is the best candidate among the five PDZ domains to recognize eye-PKC that contains a type I PDZ ligand, Ile-Thr-Ile-Ile, at its carboxyl terminus. Replacement of Ile(-3) in eye-PKC with charged residues resulted in a drastic reduction of the PDZ2 interaction. Substitution of a conserved His with Arg at the second alpha-helix of PDZ2 led to a reduced binding; however, a Leu replacement resulted in an enhanced eye-PKC association. We isolated and sequenced the InaD gene. The coding sequence of InaD contains nine exons spanning 3 kilobases. Translation of coding sequences from three wild-type alleles revealed three SNPs affecting residues, 282, 319, and 333 of INAD. These polymorphisms are localized in PDZ2. Interestingly, we found two of three PDZ2 variants displayed a greater affinity for eye-PKC. In summary, we evaluated the molecular basis of the eye-PKC and PDZ2 association by mutational analysis and concluded that PDZ2 of INAD is a type I domain important for the eye-PKC interaction.
authors.affiliation: Department of Pharmacology and Center for Molecular Neuroscience, Vanderbilt University, Nashville, TN 37232-6600, USA.
authors.forename: R
authors.initials: R
authors.lastname: Kumar
authors.forename: B H
authors.initials: BH
authors.lastname: Shieh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004330:Drosophila; D029721:Drosophila Proteins; D005123:Eye / Q000201:enzymology*; D005136:Eye Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011493:Protein Kinase C / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D029721:Drosophila Proteins; D005136:Eye Proteins; C091568:inaD protein, Drosophila; D011493:Protein Kinase C