title: Crystal structure of glucoamylase from Aspergillus awamori var. X100 to 2.2-A resolution.
abstract: The crystal structure of a catalytically active fragment of glucoamylase-I from Aspergillus awamori var. X100 has been determined to a resolution of 2.2 A. Twelve of its 13 alpha-helices are arranged into an "alpha/alpha-barrel." An inner core of six mutually parallel alpha-helices are connected to each other through a peripheral set of six alpha-helices. The peripheral helices are parallel to each other, but approximately antiparallel to the inner core of alpha-helices. The putative active site lies in the packing void of the inner set of helices. The last 30 residues of the enzyme comprise a separate domain containing 10 sites of O-glycosylation. Each instance of O-glycosylation involves a serine or threonine side chain linked to the alpha-anomer of a single mannosyl residue. The O-glycosylated domain is in an extended conformation, wrapping around the "waist" of the alpha/alpha-barrel. Two additional sites of N-glycosylation contribute well ordered glycosyl chains that lie in proximity to the belt of O-glycosylation. The model developed for glucoamylase is a rare and valuable structural example of a glycoprotein and an exo-acting amylolytic enzyme.
authors.affiliation: Department of Molecular Biology, Leningrad Nuclear Physics Institute, St. Petersburg, Russia.
authors.forename: A
authors.initials: A
authors.lastname: Aleshin
authors.forename: A
authors.initials: A
authors.lastname: Golubev
authors.forename: L M
authors.initials: LM
authors.lastname: Firsov
authors.forename: R B
authors.initials: RB
authors.lastname: Honzatko
mesh_terms: D000595:Amino Acid Sequence; D001230:Aspergillus / Q000201:enzymology*; D002240:Carbohydrate Sequence; D003461:Crystallography; D005087:Glucan 1,4-alpha-Glucosidase / Q000737:chemistry / Q000648:ultrastructure*; D006023:Glycoproteins / Q000737:chemistry / Q000648:ultrastructure; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D006023:Glycoproteins; D010446:Peptide Fragments; D005087:Glucan 1,4-alpha-Glucosidase