title: A novel structural fold in polysaccharide lyases: Bacillus subtilis family 11 rhamnogalacturonan lyase YesW with an eight-bladed beta-propeller.
abstract: Rhamnogalacturonan (RG) lyase produced by plant pathogenic and saprophytic microbes plays an important role in degrading plant cell walls. An extracellular RG lyase YesW from saprophytic Bacillus subtilis is a member of polysaccharide lyase family 11 and cleaves glycoside bonds in polygalacturonan as well as RG type-I through a beta-elimination reaction. Crystal structures of YesW and its complex with galacturonan disaccharide, a reaction product analogue, were determined at 1.4 and 2.5 A resolutions with final R-factors of 16.4% and 16.6%, respectively. The enzyme is composed of an eight-bladed beta-propeller with a deep cleft in the center as a basic scaffold, and its structural fold has not been seen in polysaccharide lyases analyzed thus far. Structural analysis of the disaccharide-bound YesW and a site-directed mutagenesis study suggested that Arg-452 and Lys-535 stabilize the carboxyl group of the acidic polysaccharide molecule and Tyr-595 makes a stack interaction with the sugar pyranose ring. In addition to amino acid residues binding to the disaccharide, one calcium ion, which is coordinated by Asp-401, Glu-422, His-363, and His-399, may mediate the enzyme activity. This is, to our knowledge, the first report of a new structural category with a beta-propeller fold in polysaccharide lyases and provides structural insights into substrate binding by RG lyase.
authors.affiliation: Laboratory of Basic and Applied Molecular Biotechnology, Graduate School of Agriculture, Kyoto University, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Ochiai
authors.forename: Takafumi
authors.initials: T
authors.lastname: Itoh
authors.forename: Yukie
authors.initials: Y
authors.lastname: Maruyama
authors.forename: Akiko
authors.initials: A
authors.lastname: Kawamata
authors.forename: Bunzo
authors.initials: B
authors.lastname: Mikami
authors.forename: Wataru
authors.initials: W
authors.lastname: Hashimoto
authors.forename: Kousaku
authors.initials: K
authors.lastname: Murata
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D004187:Disaccharides / Q000737:chemistry / Q000378:metabolism; D020125:Mutation, Missense; D011133:Polysaccharide-Lyases / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D017433:Protein Structure, Secondary / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004187:Disaccharides; D011133:Polysaccharide-Lyases; D002118:Calcium