title: High-resolution structure of exo-arabinanase from Penicillium chrysogenum.
abstract: Arabinanase Abnx from Penicillium chrysogenum 31B, which belongs to the GH93 family, releases arabinobiose from the nonreducing terminus of α-1,5-L-arabinan, which is distributed in the primary cell walls of higher plants. Crystal structures of Abnx and of its complex with arabinobiose were determined at the high resolutions of 1.14 Å to an R(work) of 10.7% (R(free) = 12.8%) and 1.04 Å to an R(work) of 10.4% (R(free) = 12.5%). Abnx has a six-bladed β-propeller fold with a typical ring-closure mode called `Velcro', in which the last four-stranded β-sheet is completed by the incorporation of a strand from the N-terminus. Catalytic residues which act as a nucleophile and an acid/base were proposed from the structures and confirmed by site-directed mutagenesis. The substrate-binding groove is enclosed at one end by two residues, Glu64 and Tyr66, which contribute to the recognition of the nonreducing chain end of the polysaccharide. A comparison with the related enzyme Arb93A which has a quite similar overall structure suggested that Abnx has different mechanisms to funnel substrates to the active site and/or to stabilize the transition state.
authors.affiliation: Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Sogabe
authors.forename: Tomoya
authors.initials: T
authors.lastname: Kitatani
authors.forename: Asako
authors.initials: A
authors.lastname: Yamaguchi
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Kinoshita
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Adachi
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Takano
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Inoue
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Mori
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Matsumura
authors.forename: Tatsuji
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Toshiji
authors.initials: T
authors.lastname: Tada
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D004187:Disaccharides / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D010408:Penicillium chrysogenum / Q000737:chemistry / Q000201:enzymology*; D011487:Protein Conformation; D013379:Substrate Specificity
chemical_list: D004187:Disaccharides; C434937:arabinobiose; D006026:Glycoside Hydrolases; C434938:exo-alpha-L-arabinanase