Structural and Mutational Characterization of the Catalytic A-module of the Mannuronan C-5-epimerase AlgE4 from Azotobacter vinelandii
Autor: | Rozeboom, Henriette J., Bjerkan, Tonje M., Kalk, Kor H., Ertesvag, Helga, Holtan, Synnove, Aachmann, Finn L., Valla, Svein, Dijkstra, Bauke W., Ertesvåg, Helga, Holtan, Synnøve |
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Přispěvatelé: | Groningen Biomolecular Sciences and Biotechnology, X-ray Crystallography |
Rok vydání: | 2008 |
Předmět: |
ANGSTROM RESOLUTION
PROTEIN C-5 EPIMERASE ALGE4 ASPERGILLUS-NIGER Isomerase Crystallography X-Ray Biochemistry Protein Structure Secondary Catalytic Domain ALGINATE LYASE A1-III CRYSTAL-STRUCTURE Molecular Biology Protein secondary structure chemistry.chemical_classification Azotobacter vinelandii SECONDARY STRUCTURE biology ACTIVE-SITE Mutagenesis PSEUDOMONAS-AERUGINOSA ELECTRON-DENSITY MAPS Active site Cell Biology biology.organism_classification Amino acid N-terminus Crystallography chemistry Structural Homology Protein Protein Structure and Folding biology.protein Epimer Carbohydrate Epimerases |
Zdroj: | The Journal of Biological Chemistry, 283(35), 23819-23828. AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC |
ISSN: | 0021-9258 |
Popis: | Alginate is a family of linear copolymers of (1 -> 4)-linked beta-D-mannuronic acid and its C-5 epimer alpha-L-guluronic acid. The polymer is first produced as polymannuronic acid and the guluronic acid residues are then introduced at the polymer level by mannuronan C-5-epimerases. The structure of the catalytic A-module of the Azotobacter vinelandii mannuronan C-5-epimerase AlgE4 has been determined by x-ray crystallography at 2.1-angstrom resolution. AlgE4A folds into a right-handed parallel beta-helix structure originally found in pectate lyase C and subsequently in several polysaccharide lyases and hydrolases. The beta-helix is composed of four parallel beta-sheets, comprising 12 complete turns, and has an amphipathic alpha-helix near the N terminus. The catalytic site is positioned in a positively charged cleft formed by loops extending from the surface encompassing Asp(152), an amino acid previously shown to be important for the reaction. Site-directed mutagenesis further implicates Tyr(149), His(154), and Asp(178) as being essential for activity. Tyr(149) probably acts as the proton acceptor, whereas His(154) is the proton donor in the epimerization reaction. |
Databáze: | OpenAIRE |
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