A/NWS/whale/Maine/1/84 (H1N9) reassortant influenza virus neuraminidase
[NRAM_I84A1] Catalyzes the removal of terminal sialic acid residues from viral and cellular glycoconjugates. Cleaves off the terminal sialic acids on the glycosylated HA during virus budding to facilitate virus release. Additionally helps virus spread through the circulation by further removing sialic acids from the cell surface. These cleavages prevent self-aggregation and ensure the efficient spread of the progeny virus from cell to cell. Otherwise, infection would be limited to one round of replication. Described as a receptor-destroying enzyme because it cleaves a terminal sialic acid from the cellular receptors. May facilitate viral invasion of the upper airways by cleaving the sialic acid moities on the mucin of the airway epithelial cells. Likely to plays a role in the budding process through its association with lipid rafts during intracellular transport. May additionally display a raft-association independent effect on budding. Plays a role in the determination of host range restriction on replication and virulence. Sialidase activity in late endosome/lysosome traffic seems to enhance virus replication.
Publication Abstract from PubMed
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.
Structure of a calcium-deficient form of influenza virus neuraminidase: implications for substrate binding.,Smith BJ, Huyton T, Joosten RP, McKimm-Breschkin JL, Zhang JG, Luo CS, Lou MZ, Labrou NE, Garrett TP Acta Crystallogr D Biol Crystallogr. 2006 Sep;62(Pt 9):947-52. Epub 2006, Aug 19. PMID:16929094
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.