title: Structures of trehalose synthase from Deinococcus radiodurans reveal that a closed conformation is involved in catalysis of the intramolecular isomerization.
abstract: Trehalose synthase catalyzes the simple conversion of the inexpensive maltose into trehalose with a side reaction of hydrolysis. Here, the crystal structures of the wild type and the N253A mutant of Deinococcus radiodurans trehalose synthase (DrTS) in complex with the inhibitor Tris are reported. DrTS consists of a catalytic (β/α)8 barrel, subdomain B, a C-terminal β domain and two TS-unique subdomains (S7 and S8). The C-terminal domain and S8 contribute the majority of the dimeric interface. DrTS shares high structural homology with sucrose hydrolase, amylosucrase and sucrose isomerase in complex with sucrose, in particular a virtually identical active-site architecture and a similar substrate-induced rotation of subdomain B. The inhibitor Tris was bound and mimics a sugar at the -1 subsite. A maltose was modelled into the active site, and subsequent mutational analysis suggested that Tyr213, Glu320 and Glu324 are essential within the +1 subsite for the TS activity. In addition, the interaction networks between subdomains B and S7 seal the active-site entrance. Disruption of such networks through the replacement of Arg148 and Asn253 with alanine resulted in a decrease in isomerase activity by 8-9-fold and an increased hydrolase activity by 1.5-1.8-fold. The N253A structure showed a small pore created for water entry. Therefore, our DrTS-Tris may represent a substrate-induced closed conformation that will facilitate intramolecular isomerization and minimize disaccharide hydrolysis.
authors.affiliation: Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 11221, Taiwan.
authors.forename: Yung Lin
authors.initials: YL
authors.lastname: Wang
authors.affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 11221, Taiwan.
authors.forename: Sih Yao
authors.initials: SY
authors.lastname: Chow
authors.affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 11221, Taiwan.
authors.forename: Yi Ting
authors.initials: YT
authors.lastname: Lin
authors.affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 11221, Taiwan.
authors.forename: Yu Chiao
authors.initials: YC
authors.lastname: Hsieh
authors.affiliation: Department of Life Sciences, National Taiwan Normal University, Taipei 11677, Taiwan.
authors.forename: Guan Chiun
authors.initials: GC
authors.lastname: Lee
authors.affiliation: Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 11221, Taiwan.
authors.forename: Shwu Huey
authors.initials: SH
authors.lastname: Liaw
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D034301:Deinococcus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007536:Isomerism; D008320:Maltose / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017354:Point Mutation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D008320:Maltose; D005964:Glucosyltransferases; C099692:trehalose synthase
keywords: conformational change; enzyme mechanism; glycoside hydrolase family 13; intramolecular isomerization; trehalose synthase