title: Bacillus licheniformis trehalose-6-phosphate hydrolase structures suggest keys to substrate specificity.
abstract: Trehalose-6-phosphate hydrolase (TreA) belongs to glycoside hydrolase family 13 (GH13) and catalyzes the hydrolysis of trehalose 6-phosphate (T6P) to yield glucose and glucose 6-phosphate. The products of this reaction can be further metabolized by the energy-generating glycolytic pathway. Here, crystal structures of Bacillus licheniformis TreA (BlTreA) and its R201Q mutant complexed with p-nitrophenyl-α-D-glucopyranoside (R201Q-pPNG) are presented at 2.0 and 2.05 Å resolution, respectively. The overall structure of BlTreA is similar to those of other GH13 family enzymes. However, detailed structural comparisons revealed that the catalytic site of BlTreA contains a long loop that adopts a different conformation from those of other GH13 family members. Unlike the homologous regions of Bacillus cereus oligo-1,6-glucosidase (BcOgl) and Erwinia rhapontici isomaltulose synthase (NX-5), the surface potential of the BlTreA active site exhibits a largely positive charge contributed by the four basic residues His281, His282, Lys284 and Lys292. Mutation of these residues resulted in significant decreases in the enzymatic activity of BlTreA. Strikingly, the (281)HHLK(284) motif and Lys292 play critical roles in substrate discrimination by BlTreA.
authors.affiliation: Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu 300, Taiwan.
authors.forename: Min Guan
authors.initials: MG
authors.lastname: Lin
authors.affiliation: Department of Applied Chemistry, National Chiayi University, Chiayi 600, Taiwan.
authors.forename: Meng Chun
authors.initials: MC
authors.lastname: Chi
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Vankadari
authors.initials: V
authors.lastname: Naveen
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Yi Ching
authors.initials: YC
authors.lastname: Li
authors.affiliation: Department of Applied Chemistry, National Chiayi University, Chiayi 600, Taiwan.
authors.forename: Long Liu
authors.initials: LL
authors.lastname: Lin
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Chwan Deng
authors.initials: CD
authors.lastname: Hsiao
mesh_terms: D000595:Amino Acid Sequence; D001407:Bacillus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004186:Disaccharidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005960:Glucosides / Q000378:metabolism; D017354:Point Mutation; D011487:Protein Conformation; D016415:Sequence Alignment
chemical_list: D005960:Glucosides; C019502:4-nitrophenyl alpha-glucoside; D004186:Disaccharidases; C040631:alpha, alpha-phosphotrehalase
keywords: X-ray crystallography; glycoside hydrolase family 13; trehalose-6-phosphate hydrolase