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Q8BAC4 (M2_I18A0) Reviewed, UniProtKB/Swiss-Prot

Last modified April 16, 2014. Version 43. Feed History...

Clusters with 100%, 90%, 50% identity | Documents (1) | Third-party data text xml rdf/xml gff fasta
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Names and origin

Protein namesRecommended name:
Matrix protein 2
Alternative name(s):
Proton channel protein M2
Gene names
Name:M
OrganismInfluenza A virus (strain A/Brevig Mission/1/1918 H1N1) (Influenza A virus (strain A/South Carolina/1/1918 H1N1)) [Complete proteome]
Taxonomic identifier88776 [NCBI]
Taxonomic lineageVirusesssRNA negative-strand virusesOrthomyxoviridaeInfluenzavirus A
Virus hostAves [TaxID: 8782]
Homo sapiens (Human) [TaxID: 9606]
Sus scrofa (Pig) [TaxID: 9823]

Protein attributes

Sequence length97 AA.
Sequence statusComplete.
Protein existenceInferred from homology

General annotation (Comments)

Function

Forms a proton-selective ion channel that is necessary for the efficient release of the viral genome during virus entry. After attaching to the cell surface, the virion enters the cell by endocytosis. Acidification of the endosome triggers M2 ion channel activity. The influx of protons into virion interior is believed to disrupt interactions between the viral ribonucleoprotein (RNP), matrix protein 1 (M1), and lipid bilayers, thereby freeing the viral genome from interaction with viral proteins and enabling RNA segments to migrate to the host cell nucleus, where influenza virus RNA transcription and replication occur. Also plays a role in viral proteins secretory pathway. Elevates the intravesicular pH of normally acidic compartments, such as trans-Golgi network, preventing newly formed hemagglutinin from premature switching to the fusion-active conformation By similarity.

Enzyme regulation

The M2 protein from most influenza A strains is inhibited by amantadine and rimantadine, resulting in viral uncoating incapacity. Emergence of amantadine-resistant variants is usually rapid By similarity.

Subunit structure

Homotetramer; composed of two disulfide-linked dimers held together by non-covalent interactions By similarity. May interact with matrix protein 1.

Subcellular location

Virion membrane. Host apical cell membrane; Single-pass type III membrane protein. Note: Abundantly expressed at the apical plasma membrane in infected polarized epithelial cells, in close proximity to budding and assembled virions. Minor component of virions (only 16-20 molecules/virion) By similarity.

Domain

Cytoplasmic tail plays an important role in virion assembly and morphogenesis By similarity.

Miscellaneous

When the channel is activated, one or more imidazole moities of His-37 probably become bi-protonated.

South Carolina isolate has been sequenced from formalid fixed-lung tissues of a 21-year-old male which died in 1918 at Ft. Jackson, SC. Brevig Mission isolate has been sequenced from lung tissues of an Inuit woman buried in the permafrost in a gravesite near Brevig Mission, Alaska. This sample was recovered by John Hultin, retired pathologist.

Sequence similarities

Belongs to the influenza viruses matrix protein M2 family.

Alternative products

This entry describes 2 isoforms produced by alternative splicing. [Align] [Select]

Note: Only the first 9 residues are shared by the 2 isoforms.
Isoform M2 (identifier: Q8BAC4-1)

This isoform has been chosen as the 'canonical' sequence. All positional information in this entry refers to it. This is also the sequence that appears in the downloadable versions of the entry.
Isoform M1 (identifier: Q8BAC3-1)

The sequence of this isoform can be found in the external entry Q8BAC3.
Isoforms of the same protein are often annotated in two different entries if their sequences differ significantly.

Sequence annotation (Features)

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifier

Molecule processing

Chain1 – 9797Matrix protein 2
PRO_0000310566

Regions

Topological domain1 – 2222Virion surface Potential
Transmembrane23 – 4321Helical; Potential
Topological domain44 – 9754Intravirion Potential

Sites

Site371Essential for channel activity, seems to be protonated during channel activation, and may play a role in the channel gating and selectivity By similarity
Site411Seems to be involved in pH gating By similarity

Amino acid modifications

Modified residue641Phosphoserine; by host By similarity
Lipidation501S-palmitoyl cysteine; by host By similarity
Glycosylation201N-linked (GlcNAc...); by host Potential
Disulfide bond17Interchain (with C-17) By similarity
Disulfide bond19Interchain (with C-19) By similarity

Experimental info

Sequence conflict61 – 633RGP → EGL in AAC57067. Ref.2

Sequences

Sequence LengthMass (Da)Tools
Isoform M2 [UniParc].

Last modified March 1, 2003. Version 1.
Checksum: ADBB522C7F5E85FB

FASTA9711,213
        10         20         30         40         50         60 
MSLLTEVETP TRNEWGCRCN DSSDPLVIAA SIIGILHLIL WILDRLFFKC IYRRLKYGLK 

        70         80         90 
RGPSTEGVPE SMREEYRKEQ QSAVDVDDGH FVNIELE 

« Hide

Isoform M1 [UniParc].

See Q8BAC3.

References

[1]"Characterization of the 1918 'Spanish' influenza virus matrix gene segment."
Reid A.H., Fanning T.G., Janczewski T.A., McCall S., Taubenberger J.K.
J. Virol. 76:10717-10723(2002) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [GENOMIC RNA].
[2]"Initial genetic characterization of the 1918 'Spanish' influenza virus."
Taubenberger J.K., Reid A.H., Krafft A.E., Bijwaard K.E., Fanning T.G.
Science 275:1793-1796(1997) [PubMed] [Europe PMC] [Abstract]
Cited for: NUCLEOTIDE SEQUENCE [GENOMIC RNA] OF 38-63.
Strain: A/South Carolina/1/18.

Cross-references

Sequence databases

EMBL
GenBank
DDBJ
AY130766 Genomic RNA. Translation: AAN06598.1.
U94897 Genomic RNA. Translation: AAC57067.1.

3D structure databases

ProteinModelPortalQ8BAC4.
SMRQ8BAC4. Positions 23-60.
ModBaseSearch...
MobiDBSearch...

Protocols and materials databases

StructuralBiologyKnowledgebaseSearch...

Family and domain databases

InterProIPR002089. Flu_M2.
[Graphical view]
PfamPF00599. Flu_M2. 1 hit.
[Graphical view]
ProDomPD001031. Flu_M2. 1 hit.
[Graphical view] [Entries sharing at least one domain]
ProtoNetSearch...

Entry information

Entry nameM2_I18A0
AccessionPrimary (citable) accession number: Q8BAC4
Secondary accession number(s): O10622
Entry history
Integrated into UniProtKB/Swiss-Prot: November 13, 2007
Last sequence update: March 1, 2003
Last modified: April 16, 2014
This is version 43 of the entry and version 1 of the sequence. [Complete history]
Entry statusReviewed (UniProtKB/Swiss-Prot)
Annotation programViral Protein Annotation Program

Relevant documents

SIMILARITY comments

Index of protein domains and families