title: Structure of the homodimeric glycine decarboxylase P-protein from Synechocystis sp. PCC 6803 suggests a mechanism for redox regulation.
abstract: Glycine decarboxylase, or P-protein, is a pyridoxal 5'-phosphate (PLP)-dependent enzyme in one-carbon metabolism of all organisms, in the glycine and serine catabolism of vertebrates, and in the photorespiratory pathway of oxygenic phototrophs. P-protein from the cyanobacterium Synechocystis sp. PCC 6803 is an α2 homodimer with high homology to eukaryotic P-proteins. The crystal structure of the apoenzyme shows the C terminus locked in a closed conformation by a disulfide bond between Cys(972) in the C terminus and Cys(353) located in the active site. The presence of the disulfide bridge isolates the active site from solvent and hinders the binding of PLP and glycine in the active site. Variants produced by substitution of Cys(972) and Cys(353) by Ser using site-directed mutagenesis have distinctly lower specific activities, supporting the crucial role of these highly conserved redox-sensitive amino acid residues for P-protein activity. Reduction of the 353-972 disulfide releases the C terminus and allows access to the active site. PLP and the substrate glycine bind in the active site of this reduced enzyme and appear to cause further conformational changes involving a flexible surface loop. The observation of the disulfide bond that acts to stabilize the closed form suggests a molecular mechanism for the redox-dependent activation of glycine decarboxylase observed earlier.
authors.affiliation: From the Department of Cell and Molecular Biology, Uppsala University, S-751 24 Uppsala, Sweden.
authors.forename: Dirk
authors.initials: D
authors.lastname: Hasse
authors.forename: Evalena
authors.initials: E
authors.lastname: Andersson
authors.forename: Gunilla
authors.initials: G
authors.lastname: Carlsson
authors.forename: Axel
authors.initials: A
authors.lastname: Masloboy
authors.forename: Martin
authors.initials: M
authors.lastname: Hagemann
authors.forename: Hermann
authors.initials: H
authors.lastname: Bauwe
authors.forename: Inger
authors.initials: I
authors.lastname: Andersson
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D050841:Glycine Dehydrogenase (Decarboxylating) / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D046939:Synechocystis / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D050841:Glycine Dehydrogenase (Decarboxylating)
keywords: Crystal Structure; Decarboxylase; Disulfide; Glycine Decarboxylase; P-protein; Pyridoxal Phosphate; Redox Regulation