title: Structural characterization of the mechanism through which human glutamic acid decarboxylase auto-activates.
abstract: Imbalances in GABA (γ-aminobutyric acid) homoeostasis underlie psychiatric and movement disorders. The ability of the 65 kDa isoform of GAD (glutamic acid decarboxylase), GAD65, to control synaptic GABA levels is influenced through its capacity to auto-inactivate. In contrast, the GAD67 isoform is constitutively active. Previous structural insights suggest that flexibility in the GAD65 catalytic loop drives enzyme inactivation. To test this idea, we constructed a panel of GAD65/67 chimaeras and compared the ability of these molecules to auto-inactivate. Together, our data reveal the important finding that the C-terminal domain of GAD plays a key role in controlling GAD65 auto-inactivation. In support of these findings, we determined the X-ray crystal structure of a GAD65/67 chimaera that reveals that the conformation of the catalytic loop is intimately linked to the C-terminal domain.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, VIC 3800, Australia.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Langendorf
authors.forename: Kellie L
authors.initials: KL
authors.lastname: Tuck
authors.forename: Trevor L G
authors.initials: TL
authors.lastname: Key
authors.forename: Gustavo
authors.initials: G
authors.lastname: Fenalti
authors.forename: Robert N
authors.initials: RN
authors.lastname: Pike
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Rosado
authors.forename: Anders S M
authors.initials: AS
authors.lastname: Wong
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Buckle
authors.forename: Ruby H P
authors.initials: RH
authors.lastname: Law
authors.forename: James C
authors.initials: JC
authors.lastname: Whisstock
mesh_terms: D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D004795:Enzyme Stability; D005968:Glutamate Decarboxylase / Q000737:chemistry*; D018698:Glutamic Acid / Q000737:chemistry; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics; D015203:Reproducibility of Results; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics
chemical_list: D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D018698:Glutamic Acid; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1; C401141:glutamate decarboxylase 2