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Influenza A virus (strain A/Duck/Alberta/28/1976 H4N6)
Reviewed-Annotation score: Annotation score: 4 out of 5-Protein inferred from homologyi


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.


The influenza A genome consist of 8 RNA segments. Genetic variation of hemagglutinin and/or neuraminidase genes results in the emergence of new influenza strains. The mechanism of variation can be the result of point mutations or the result of genetic reassortment between segments of two different strains.

Catalytic activityi

Hydrolysis of alpha-(2->3)-, alpha-(2->6)-, alpha-(2->8)- glycosidic linkages of terminal sialic acid residues in oligosaccharides, glycoproteins, glycolipids, colominic acid and synthetic substrates.


Ca2+By similarityNote: Binds 1 Ca2+ ion.By similarity

Enzyme regulationi

Inhibited by the neuraminidase inhibitors zanamivir (Relenza) and oseltamivir (Tamiflu). These drugs interfere with the release of progeny virus from infected cells and are effective against all influenza strains. Resistance to neuraminidase inhibitors is quite rare.

GO - Molecular functioni

GO - Biological processi


Molecular functionGlycosidase, Hydrolase
LigandCalcium, Metal-binding

Protein family/group databases

CAZyiGH34. Glycoside Hydrolase Family 34.

Names & Taxonomyi

Protein namesi
Recommended name:
Neuraminidase (EC:
Gene namesi
OrganismiInfluenza A virus (strain A/Duck/Alberta/28/1976 H4N6)
Taxonomic identifieri385638 [NCBI]
Taxonomic lineageiVirusesssRNA virusesssRNA negative-strand virusesOrthomyxoviridaeInfluenzavirus A
Virus hostiAves [TaxID: 8782]
Sus scrofa (Pig) [TaxID: 9823]

Subcellular locationi

  • Virion membrane By similarity
  • Host apical cell membrane By similarity; Single-pass type II membrane protein By similarity

  • Note: Preferentially accumulates at the apical plasma membrane in infected polarized epithelial cells, which is the virus assembly site. Uses lipid rafts for cell surface transport and apical sorting. In the virion, forms a mushroom-shaped spike on the surface of the membrane (By similarity).By similarity


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Topological domaini1 – 6IntravirionSequence analysis6
Transmembranei7 – 35Helical; Signal-anchor for type II membrane proteinSequence analysisAdd BLAST29
Topological domaini36 – ›103Virion surfaceSequence analysisAdd BLAST›68

GO - Cellular componenti

Keywords - Cellular componenti

Host cell membrane, Host membrane, Membrane, Virion

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
ChainiPRO_00000786821 – ›103NeuraminidaseAdd BLAST›103

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Glycosylationi51N-linked (GlcNAc...) asparagine; by hostSequence analysis1
Glycosylationi54N-linked (GlcNAc...) asparagine; by hostSequence analysis1
Glycosylationi67N-linked (GlcNAc...) asparagine; by hostSequence analysis1
Glycosylationi70N-linked (GlcNAc...) asparagine; by hostSequence analysis1
Glycosylationi86N-linked (GlcNAc...) asparagine; by hostSequence analysis1

Post-translational modificationi

N-glycosylated.By similarity

Keywords - PTMi



Subunit structurei

Homotetramer.By similarity


3D structure databases


Family & Domainsi


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Regioni11 – 33Involved in apical transport and lipid raft associationBy similarityAdd BLAST23
Regioni36 – 90Hypervariable stalk regionAdd BLAST55
Regioni91 – ›103Head of neuraminidaseAdd BLAST›13


Intact N-terminus is essential for virion morphogenesis. Possess two apical sorting signals, one in the ectodomain, which is likely to be a glycan, and the other in the transmembrane domain. The transmembrane domain also plays a role in lipid raft association (By similarity).By similarity

Sequence similaritiesi

Belongs to the glycosyl hydrolase 34 family.Curated

Keywords - Domaini

Signal-anchor, Transmembrane, Transmembrane helix


Sequence statusi: Fragment.

P03479-1 [UniParc]FASTAAdd to basket

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Mass (Da):11,307
Last modified:July 21, 1986 - v1

Experimental Info

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sequence conflicti22Q → L in AAA43358 (PubMed:6927853).Curated1
Non-terminal residuei1031

Sequence databases

Select the link destinations:
Links Updated
V01095 Genomic RNA. Translation: CAA24279.1.
K01009 Genomic RNA. Translation: AAA43358.1.

Similar proteinsi

Links to similar proteins from the UniProt Reference Clusters (UniRef) at 100%, 90% and 50% sequence identity:
100%UniRef100 combines identical sequences and sub-fragments with 11 or more residues from any organism into one UniRef entry.
90%UniRef90 is built by clustering UniRef100 sequences that have at least 90% sequence identity to, and 80% overlap with, the longest sequence (a.k.a seed sequence).
50%UniRef50 is built by clustering UniRef90 seed sequences that have at least 50% sequence identity to, and 80% overlap with, the longest sequence in the cluster.

Entry informationi

Entry nameiNRAM_I76A1
AccessioniPrimary (citable) accession number: P03479
Secondary accession number(s): Q84031
Entry historyiIntegrated into UniProtKB/Swiss-Prot: July 21, 1986
Last sequence update: July 21, 1986
Last modified: May 10, 2017
This is version 91 of the entry and version 1 of the sequence. See complete history.
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programViral Protein Annotation Program



  1. Glycosyl hydrolases
    Classification of glycosyl hydrolase families and list of entries
  2. SIMILARITY comments
    Index of protein domains and families