title: Structure of novel enzyme in mannan biodegradation process 4-O-β-D-mannosyl-D-glucose phosphorylase MGP.
abstract: The crystal structure of a novel component of the mannan biodegradation system, 4-O-β-D-mannosyl-D-glucose phosphorylase (MGP), was determined to a 1.68-Å resolution. The structure of the enzyme revealed a unique homohexameric structure, which was formed by using two helices attached to the N-terminus and C-terminus as a tab for sticking between subunits. The structures of MGP complexes with genuine substrates, 4-O-β-D-mannosyl-D-glucose and phosphate, and the product D-mannose-1-phosphate were also determined. The complex structures revealed that the invariant residue Asp131, which is supposed to be the general acid/base, did not exist close to the glycosidic Glc-O4 atom, which should be protonated in the catalytic reaction. Also, no solvent molecule that might mediate a proton transfer from Asp131 was observed in the substrate complex structure, suggesting that the catalytic mechanism of MGP is different from those of known disaccharide phosphorylases.
authors: Department of Bioscience, Nagahama Institute of Bio-science and Technology, and Japan Science and Technology Agency Institute for Bioinformatics Research and Development, 1266 Tamura, Nagahama 526-0829, Japan.
authors: Setsu
authors: S
authors: Nakae
authors: Shigeaki
authors: S
authors: Ito
authors: Mariko
authors: M
authors: Higa
authors: Takeshi
authors: T
authors: Senoura
authors: Jun
authors: J
authors: Wasaki
authors: Atsushi
authors: A
authors: Hijikata
authors: Masafumi
authors: M
authors: Shionyu
authors: Susumu
authors: S
authors: Ito
authors: Tsuyoshi
authors: T
authors: Shirai
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D020134:Catalytic Domain; D005947:Glucose / Q000737:chemistry / Q000378:metabolism; D008351:Mannans / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D006005:Phosphorylases / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D008351:Mannans; D021122:Protein Subunits; D006005:Phosphorylases; D005947:Glucose
keywords: X-ray crystallography; biomass degradation; hemicellulose; protein evolution