title: Crystal structure of the GAF-B domain from human phosphodiesterase 10A complexed with its ligand, cAMP.
abstract: Cyclic nucleotide phosphodiesterases (PDEs) catalyze the degradation of the cyclic nucleotides cAMP and cGMP, which are important second messengers. Five of the 11 mammalian PDE families have tandem GAF domains at their N termini. PDE10A may be the only mammalian PDE for which cAMP is the GAF domain ligand, and it may be allosterically stimulated by cAMP. PDE10A is highly expressed in striatal medium spiny neurons. Here we report the crystal structure of the C-terminal GAF domain (GAF-B) of human PDE10A complexed with cAMP at 2.1-angstroms resolution. The conformation of the PDE10A GAF-B domain monomer closely resembles those of the GAF domains of PDE2A and the cyanobacterium Anabaena cyaB2 adenylyl cyclase, except for the helical bundle consisting of alpha1, alpha2, and alpha5. The PDE10A GAF-B domain forms a dimer in the crystal and in solution. The dimerization is mainly mediated by hydrophobic interactions between the helical bundles in a parallel arrangement, with a large buried surface area. In the PDE10A GAF-B domain, cAMP tightly binds to a cNMP-binding pocket. The residues in the alpha3 and alpha4 helices, the beta6 strand, the loop between 3(10) and alpha4, and the loop between alpha4 and beta5 are involved in the recognition of the phosphate and ribose moieties. This recognition mode is similar to those of the GAF domains of PDE2A and cyaB2. In contrast, the adenine base is specifically recognized by the PDE10A GAF-B domain in a unique manner, through residues in the beta1 and beta2 strands.
authors.affiliation: Systems and Structural Biology Center, Yokohama Institute, RIKEN, Yokohama 230-0045, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Handa
authors.forename: Eiichi
authors.initials: E
authors.lastname: Mizohata
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Kishishita
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Toyama
authors.forename: Satoshi
authors.initials: S
authors.lastname: Morita
authors.forename: Tomomi
authors.initials: T
authors.lastname: Uchikubo-Kamo
authors.forename: Ryogo
authors.initials: R
authors.lastname: Akasaka
authors.forename: Kenji
authors.initials: K
authors.lastname: Omori
authors.forename: Jun
authors.initials: J
authors.lastname: Kotera
authors.forename: Takaho
authors.initials: T
authors.lastname: Terada
authors.forename: Mikako
authors.initials: M
authors.lastname: Shirouzu
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D017033:Anabaena / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites / Q000502:physiology; D018360:Crystallography, X-Ray; D000242:Cyclic AMP / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006152:Cyclic GMP / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D054678:Cyclic Nucleotide Phosphodiesterases, Type 2 / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D006801:Humans; D009474:Neurons / Q000201:enzymology; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D040681:Structural Homology, Protein; D014793:Visual Cortex / Q000201:enzymology
chemical_list: D001426:Bacterial Proteins; D000242:Cyclic AMP; C119843:PDE10A protein, human; D010727:Phosphoric Diester Hydrolases; D054678:Cyclic Nucleotide Phosphodiesterases, Type 2; C517275:PDE2A protein, human; D006152:Cyclic GMP