title: Structure of a calcium-deficient form of influenza virus neuraminidase: implications for substrate binding.
abstract: The X-ray structure of influenza virus neuraminidase (NA) isolated from whale, subtype N9, has been determined at 2.2 A resolution and contains a tetrameric protein in the asymmetric unit. In structures of NA determined previously, a calcium ion is observed to coordinate amino acids near the substrate-binding site. In three of the NA monomers determined here this calcium is absent, resulting in structural alterations near the substrate-binding site. These changes affect the conformation of residues that participate in several key interactions between the enzyme and substrate and provide at a molecular level the basis of the structural and functional role of calcium in substrate and inhibitor binding. Several sulfate ions were identified in complex with the protein. These are located in the active site, occupying the space reserved for the substrate (sialic acid) carboxylate, and in positions leading away from the substrate-binding site. These sites offer a new opportunity for the design of inhibitors of influenza virus NA.
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia. bsmith@wehi.edu.au
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Smith
authors.forename: Trevor
authors.initials: T
authors.lastname: Huyton
authors.forename: Robbie P
authors.initials: RP
authors.lastname: Joosten
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: McKimm-Breschkin
authors.forename: Jian Guo
authors.initials: JG
authors.lastname: Zhang
authors.forename: Cindy S
authors.initials: CS
authors.lastname: Luo
authors.forename: Mei Zhen
authors.initials: MZ
authors.lastname: Lou
authors.forename: Nikolaos E
authors.initials: NE
authors.lastname: Labrou
authors.forename: Thomas P J
authors.initials: TP
authors.lastname: Garrett
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007477:Ions; D008956:Models, Chemical; D008958:Models, Molecular; D009439:Neuraminidase / Q000737:chemistry*; D009975:Orthomyxoviridae / Q000201:enzymology*; D011485:Protein Binding; D011487:Protein Conformation; D013431:Sulfates / Q000737:chemistry; D014907:Whales / Q000821:virology; D014965:X-Rays
chemical_list: D007477:Ions; D013431:Sulfates; D009439:Neuraminidase; D002118:Calcium