title: Structure of the novel alpha-amylase AmyC from Thermotoga maritima.
abstract: alpha-Amylases are essential enzymes in alpha-glucan metabolism and catalyse the hydrolysis of long sugar polymers such as amylose and starch. The crystal structure of a previously unidentified amylase (AmyC) from the hyperthermophilic organism Thermotoga maritima was determined at 2.2 Angstroms resolution by means of MAD. AmyC lacks sequence similarity to canonical alpha-amylases, which belong to glycosyl hydrolase families 13, 70 and 77, but exhibits significant similarity to a group of as yet uncharacterized proteins in COG1543 and is related to glycerol hydrolase family 57 (GH-57). AmyC reveals features that are characteristic of alpha-amylases, such as a distorted TIM-barrel structure formed by seven beta-strands and alpha-helices (domain A), and two additional but less well conserved domains. The latter are domain B, which contains three helices inserted in the TIM-barrel after beta-sheet 2, and domain C, a five-helix region at the C-terminus. Interestingly, despite moderate sequence homology, structure comparison revealed significant similarities to a member of GH-57 with known three-dimensional structure, Thermococcus litoralis 4-glucanotransferase, and an even higher similarity to a structure of an enzyme of unknown function from Thermus thermophilus.
authors.affiliation: Abteilung Molekulare Strukturbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität, Göttingen, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Dickmanns
authors.forename: Meike
authors.initials: M
authors.lastname: Ballschmiter
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Liebl
authors.forename: Ralf
authors.initials: R
authors.lastname: Ficner
mesh_terms: D001419:Bacteria / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites; D003001:Cloning, Molecular; D003460:Crystallization; D023281:Genomics; D007700:Kinetics; D008958:Models, Molecular; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D012645:Selenomethionine / Q000737:chemistry; D000516:alpha-Amylases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D012645:Selenomethionine; D000516:alpha-Amylases