title: The first structure of pectate lyase belonging to polysaccharide lyase family 3.
abstract: The crystal structure of a highly alkaline low molecular weight pectate lyase (Pel-15) was determined at 1.5 A resolution by the multiple isomorphous replacement (MIR) method. This is the first pectate lyase structure from polysaccharide lyase family 3. The overall structure is a simple eight-turn right-handed parallel beta-helix domain with one long loop protruding from one side of the beta-helix. The low molecular weight of Pel-15 derives from the lack of N- and C-terminal extensions that are found in many beta-helix proteins. Although the structure has one calcium ion at pH 6.7, raising the pH to 9.5 results in the binding of an additional calcium ion. The common calcium ion found in both the pH 6.5 and 9.5 structures seems to stabilize both the beta-helix structure and the long protruding loop. The additional calcium ion found in the pH 9.5 structure alone may neutralize the acidic substrate. The region around the additional calcium ion is thought to bind to the substrate, as this region is rich in charged amino-acid residues which are required in catalysis.
authors.affiliation: Department of Biotechnology and Biomaterial Chemistry, Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan. h991401d@mbox.media.nagoya-u.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Akita
authors.forename: A
authors.initials: A
authors.lastname: Suzuki
authors.forename: T
authors.initials: T
authors.lastname: Kobayashi
authors.forename: S
authors.initials: S
authors.lastname: Ito
authors.forename: T
authors.initials: T
authors.lastname: Yamane
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D003625:Data Collection; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011133:Polysaccharide-Lyases / Q000737:chemistry* / Q000302:isolation & purification; D011487:Protein Conformation
chemical_list: D007527:Isoenzymes; D011133:Polysaccharide-Lyases; C023911:pectate lyase; D002118:Calcium