title: Crystal structure of maltooligosyltrehalose trehalohydrolase from Deinococcus radiodurans in complex with disaccharides.
abstract: Trehalose (alpha-D-glucopyranosyl-1,1-alpha-D-glucopyranose) is a non-reducing diglucoside found in various organisms that serves as a carbohydrate reserve and as an agent that protects against a variety of physical and chemical stresses. Deinococcus radiodurans possesses an alternative biosynthesis pathway for the synthesis of trehalose from maltooligosaccharides. This reaction is mediated by two enzymes: maltooligosyltrehalose synthase (MTSase) and maltooligosyltrehalose trehalohydrolase (MTHase). Here, we present the 1.1A resolution crystal structure of MTHase. It consists of three major domains: two beta-sheet domains and a conserved glycosidase (beta/alpha)8 barrel catalytic domain. Three subdomains consisting of short insertions were identified within the catalytic domain. Subsequently, structures of MTHase in complex with maltose and trehalose were obtained at 1.2 A and 1.5 A resolution, respectively. These structures reveal the importance of the three inserted subdomains in providing the key residues required for substrate recognition. Trehalose is recognised specifically in the +1 and +2 binding subsites by an extensive hydrogen-bonding network and a strong hydrophobic stacking interaction in between two aromatic residues. Moreover, upon binding to maltose, which mimics the substrate sugar chain, a major concerted conformational change traps the sugar chain in the active site. The presence of magnesium in the active site of the MTHase-maltose complex suggests that MTHase activity may be regulated by divalent cations.
authors.affiliation: Macromolecular Crystallography Group, European Synchrotron Radiation Facility, B.P. 220, 6 rue Jules Horowitz, F-38043 Grenoble Cedex, France.
authors.forename: Joanna
authors.initials: J
authors.lastname: Timmins
authors.forename: Hanna-Kirsti S
authors.initials: HK
authors.lastname: Leiros
authors.forename: Gordon
authors.initials: G
authors.lastname: Leonard
authors.forename: Ingar
authors.initials: I
authors.lastname: Leiros
authors.forename: Sean
authors.initials: S
authors.lastname: McSweeney
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D034301:Deinococcus / Q000201:enzymology*; D005959:Glucosidases / Q000737:chemistry* / Q000378:metabolism*; D008320:Maltose / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D021241:Spectrometry, Mass, Electrospray Ionization; D014199:Trehalose / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008320:Maltose; D014199:Trehalose; D005959:Glucosidases; C099156:maltooligosyl trehalose trehalohydrolase