From Proteopediaproteopedia link
THE X-RAY STRUCTURE OF A COMPLEX OF TERN N9 INFLUENZA VIRUS NEURAMINIDASE COMPLEXED WITH SIALIC ACID AT 4 DEGREES C REVEALING A SECOND SIALIC ACID BINDING SITE
[NRAM_I75A5] 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 a complex of sialic acid (Neu5Ac) with neuraminidase N9 subtype from A/tern/Australia/G70C/75 influenza virus at 4 degrees C has revealed the location of a second Neu5Ac binding site on the surface of the enzyme. At 18 degrees C, only the enzyme active site contains bound Neu5Ac. Neu5Ac binds in the second site in the chair conformation in a similar way to which it binds to hemagglutinin. The residues that interact with Neu5Ac at this second site are mostly conserved in avian strains, but not in human and swine strains, indicating that it has some as-yet-unknown biological function in birds.
Structural evidence for a second sialic acid binding site in avian influenza virus neuraminidases.,Varghese JN, Colman PM, van Donkelaar A, Blick TJ, Sahasrabudhe A, McKimm-Breschkin JL Proc Natl Acad Sci U S A. 1997 Oct 28;94(22):11808-12. PMID:9342319
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.