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Entry version 111 (07 Oct 2020)
Sequence version 1 (01 Jul 1989)
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Matrix protein 2



Influenza A virus (strain A/Fort Warren/1/1950 H1N1)
Reviewed-Annotation score:

Annotation score:4 out of 5

<p>The annotation score provides a heuristic measure of the annotation content of a UniProtKB entry or proteome. This score <strong>cannot</strong> be used as a measure of the accuracy of the annotation as we cannot define the 'correct annotation' for any given protein.<p><a href='/help/annotation_score' target='_top'>More...</a></p>
-Protein inferred from homologyi <p>This indicates the type of evidence that supports the existence of the protein. Note that the 'protein existence' evidence does not give information on the accuracy or correctness of the sequence(s) displayed.<p><a href='/help/protein_existence' target='_top'>More...</a></p>

<p>This section provides any useful information about the protein, mostly biological knowledge.<p><a href='/help/function_section' target='_top'>More...</a></p>Functioni

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.UniRule annotation


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

<p>This subsection of the <a href="">Function</a> section describes regulatory mechanisms for enzymes, transporters or microbial transcription factors, and reports the components which regulate (by activation or inhibition) the reaction.<p><a href='/help/activity_regulation' target='_top'>More...</a></p>Activity regulationi

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.


Feature keyPosition(s)DescriptionActionsGraphical viewLength
<p>This subsection describes interesting single amino acid sites on the sequence that are not defined in any other subsection. This subsection can be displayed in different sections ('Function', 'PTM / Processing', 'Pathology and Biotech') according to its content.<p><a href='/help/site' target='_top'>More...</a></p>Sitei37Essential for channel activity, possibly by being protonated during channel activation, and by forming the channel gate and the selective filterUniRule annotation1
Sitei41Seems to be involved in pH gatingUniRule annotation1

<p>The <a href="">Gene Ontology (GO)</a> project provides a set of hierarchical controlled vocabulary split into 3 categories:<p><a href='/help/gene_ontology' target='_top'>More...</a></p>GO - Molecular functioni

GO - Biological processi

<p>UniProtKB Keywords constitute a <a href="">controlled vocabulary</a> with a hierarchical structure. Keywords summarise the content of a UniProtKB entry and facilitate the search for proteins of interest.<p><a href='/help/keywords' target='_top'>More...</a></p>Keywordsi

Molecular functionIon channel, Viral ion channel
Biological processHost-virus interaction, Hydrogen ion transport, Inhibition of host autophagy by virus, Ion transport, Transport

<p>This section provides information about the protein and gene name(s) and synonym(s) and about the organism that is the source of the protein sequence.<p><a href='/help/names_and_taxonomy_section' target='_top'>More...</a></p>Names & Taxonomyi

<p>This subsection of the <a href="">Names and taxonomy</a> section provides an exhaustive list of all names of the protein, from commonly used to obsolete, to allow unambiguous identification of a protein.<p><a href='/help/protein_names' target='_top'>More...</a></p>Protein namesi
Recommended name:
Matrix protein 2UniRule annotation
Alternative name(s):
Proton channel protein M2UniRule annotation
<p>This subsection of the <a href="">Names and taxonomy</a> section indicates the name(s) of the gene(s) that code for the protein sequence(s) described in the entry. Four distinct tokens exist: 'Name', 'Synonyms', 'Ordered locus names' and 'ORF names'.<p><a href='/help/gene_name' target='_top'>More...</a></p>Gene namesi
Name:MUniRule annotation
<p>This subsection of the <a href="">Names and taxonomy</a> section provides information on the name(s) of the organism that is the source of the protein sequence.<p><a href='/help/organism-name' target='_top'>More...</a></p>OrganismiInfluenza A virus (strain A/Fort Warren/1/1950 H1N1)
<p>This subsection of the <a href="">Names and taxonomy</a> section shows the unique identifier assigned by the NCBI to the source organism of the protein. This is known as the 'taxonomic identifier' or 'taxid'.<p><a href='/help/taxonomic_identifier' target='_top'>More...</a></p>Taxonomic identifieri384525 [NCBI]
<p>This subsection of the <a href="">Names and taxonomy</a> section contains the taxonomic hierarchical classification lineage of the source organism. It lists the nodes as they appear top-down in the taxonomic tree, with the more general grouping listed first.<p><a href='/help/taxonomic_lineage' target='_top'>More...</a></p>Taxonomic lineageiVirusesRiboviriaOrthornaviraeNegarnaviricotaPolyploviricotinaInsthoviricetesArticulaviralesOrthomyxoviridaeAlphainfluenzavirus
<p>This subsection of the <a href="">Names and taxonomy</a> section only exists in viral entries and indicates the host(s) either as a specific organism or taxonomic group of organisms that are susceptible to be infected by a virus.<p><a href='/help/virus_host' target='_top'>More...</a></p>Virus hostiAves [TaxID: 8782]
Homo sapiens (Human) [TaxID: 9606]
Sus scrofa (Pig) [TaxID: 9823]

<p>This section provides information on the location and the topology of the mature protein in the cell.<p><a href='/help/subcellular_location_section' target='_top'>More...</a></p>Subcellular locationi


Feature keyPosition(s)DescriptionActionsGraphical viewLength
<p>This subsection of the <a href="">'Subcellular location'</a> section describes the subcellular compartment where each non-membrane region of a membrane-spanning protein is found.<p><a href='/help/topo_dom' target='_top'>More...</a></p>Topological domaini1 – 22Virion surfaceUniRule annotationAdd BLAST22
<p>This subsection of the <a href="">'Subcellular location'</a> section describes the extent of a membrane-spanning region of the protein. It denotes the presence of both alpha-helical transmembrane regions and the membrane spanning regions of beta-barrel transmembrane proteins.<p><a href='/help/transmem' target='_top'>More...</a></p>Transmembranei23 – 43Helical; Signal-anchor for type III membrane proteinUniRule annotationAdd BLAST21
Topological domaini44 – 97IntravirionUniRule annotationAdd BLAST54

Keywords - Cellular componenti

Host cell membrane, Host membrane, Membrane, Virion

<p>This section describes post-translational modifications (PTMs) and/or processing events.<p><a href='/help/ptm_processing_section' target='_top'>More...</a></p>PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
<p>This subsection of the 'PTM / Processing' section describes the extent of a polypeptide chain in the mature protein following processing or proteolytic cleavage.<p><a href='/help/chain' target='_top'>More...</a></p>ChainiPRO_00000788801 – 97Matrix protein 2Add BLAST97

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
<p>This subsection of the PTM / Processing":/help/ptm_processing_section section describes the positions of cysteine residues participating in disulfide bonds.<p><a href='/help/disulfid' target='_top'>More...</a></p>Disulfide bondi17Interchain (with C-17)UniRule annotation
Disulfide bondi19Interchain (with C-19)UniRule annotation
<p>This subsection of the <a href="">PTM / Processing</a> section specifies the position and type of each covalently attached glycan group (mono-, di-, or polysaccharide).<p><a href='/help/carbohyd' target='_top'>More...</a></p>Glycosylationi20N-linked (GlcNAc...) asparagine; by hostUniRule annotation1
<p>This subsection of the <a href="">PTM / Processing</a> section specifies the position(s) and the type of covalently attached lipid group(s).<p><a href='/help/lipid' target='_top'>More...</a></p>Lipidationi50S-palmitoyl cysteine; by hostUniRule annotation1
<p>This subsection of the 'PTM / Processing' section specifies the position and type of each modified residue excluding <a href="">lipids</a>, <a href="">glycans</a> and <a href="">protein cross-links</a>.<p><a href='/help/mod_res' target='_top'>More...</a></p>Modified residuei64Phosphoserine; by hostUniRule annotation1
Modified residuei82Phosphoserine; by hostUniRule annotation1

Keywords - PTMi

Disulfide bond, Glycoprotein, Lipoprotein, Palmitate, Phosphoprotein

<p>This section provides information on the quaternary structure of a protein and on interaction(s) with other proteins or protein complexes.<p><a href='/help/interaction_section' target='_top'>More...</a></p>Interactioni

<p>This subsection of the <a href="">'Interaction'</a> section provides information about the protein quaternary structure and interaction(s) with other proteins or protein complexes (with the exception of physiological receptor-ligand interactions which are annotated in the <a href="">'Function'</a> section).<p><a href='/help/subunit_structure' target='_top'>More...</a></p>Subunit structurei

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

UniRule annotation

<p>This section provides information on the tertiary and secondary structure of a protein.<p><a href='/help/structure_section' target='_top'>More...</a></p>Structurei

3D structure databases

SWISS-MODEL Repository - a database of annotated 3D protein structure models


Database of comparative protein structure models


<p>This section provides information on sequence similarities with other proteins and the domain(s) present in a protein.<p><a href='/help/family_and_domains_section' target='_top'>More...</a></p>Family & Domainsi

<p>This subsection of the 'Family and domains' section provides general information on the biological role of a domain. The term 'domain' is intended here in its wide acceptation, it may be a structural domain, a transmembrane region or a functional domain. Several domains are described in this subsection.<p><a href='/help/domain_cc' target='_top'>More...</a></p>Domaini

Cytoplasmic tail plays an important role in virion assembly and morphogenesis.UniRule annotation

<p>This subsection of the 'Family and domains' section provides information about the sequence similarity with other proteins.<p><a href='/help/sequence_similarities' target='_top'>More...</a></p>Sequence similaritiesi

Belongs to the influenza viruses matrix protein M2 family.UniRule annotation

Keywords - Domaini

Signal-anchor, Transmembrane, Transmembrane helix

Family and domain databases

HAMAP database of protein families

MF_04069, INFV_M2, 1 hit

Integrated resource of protein families, domains and functional sites

View protein in InterPro
IPR002089, Flu_M2

Pfam protein domain database

View protein in Pfam
PF00599, Flu_M2, 1 hit

<p>This section displays by default the canonical protein sequence and upon request all isoforms described in the entry. It also includes information pertinent to the sequence(s), including <a href="">length</a> and <a href="">molecular weight</a>. The information is filed in different subsections. The current subsections and their content are listed below:<p><a href='/help/sequences_section' target='_top'>More...</a></p>Sequences (2)i

<p>This subsection of the <a href="">Sequence</a> section indicates if the <a href="">canonical sequence</a> displayed by default in the entry is complete or not.<p><a href='/help/sequence_status' target='_top'>More...</a></p>Sequence statusi: Complete.

This entry describes 2 <p>This subsection of the 'Sequence' section lists the alternative protein sequences (isoforms) that can be generated from the same gene by a single or by the combination of up to four biological events (alternative promoter usage, alternative splicing, alternative initiation and ribosomal frameshifting). Additionally, this section gives relevant information on each alternative protein isoform. This section is only present in reviewed entries, i.e. in UniProtKB/Swiss-Prot.<p><a href='/help/alternative_products' target='_top'>More...</a></p> isoformsi produced by alternative splicing. AlignAdd to basket
Note: Only the first 9 residues are shared by the 2 isoforms.
Isoform M2 (identifier: P10921-1) [UniParc]FASTAAdd to basket

This isoform has been chosen as the <div> <p><b>What is the canonical sequence?</b><p><a href='/help/canonical_and_isoforms' target='_top'>More...</a></p>canonicali sequence. All positional information in this entry refers to it. This is also the sequence that appears in the downloadable versions of the entry.

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60 70 80 90
Mass (Da):11,178
Last modified:July 1, 1989 - v1
<p>The checksum is a form of redundancy check that is calculated from the sequence. It is useful for tracking sequence updates.</p> <p>It should be noted that while, in theory, two different sequences could have the same checksum value, the likelihood that this would happen is extremely low.</p> <p>However UniProtKB may contain entries with identical sequences in case of multiple genes (paralogs).</p> <p>The checksum is computed as the sequence 64-bit Cyclic Redundancy Check value (CRC64) using the generator polynomial: x<sup>64</sup> + x<sup>4</sup> + x<sup>3</sup> + x + 1. The algorithm is described in the ISO 3309 standard. </p> <p class="publication">Press W.H., Flannery B.P., Teukolsky S.A. and Vetterling W.T.<br /> <strong>Cyclic redundancy and other checksums</strong><br /> <a href="">Numerical recipes in C 2nd ed., pp896-902, Cambridge University Press (1993)</a>)</p> Checksum:i3CD02057E22994A4
Isoform M1 (identifier: P69275-1) [UniParc]FASTAAdd to basket
The sequence of this isoform can be found in the external entry P69275.
Isoforms of the same protein are often annotated in two different entries if their sequences differ significantly.
Mass (Da):27,903

Sequence databases

Select the link destinations:

EMBL nucleotide sequence database


GenBank nucleotide sequence database


DNA Data Bank of Japan; a nucleotide sequence database

Links Updated
X08091 Genomic RNA Translation: CAA30889.1

Keywords - Coding sequence diversityi

Alternative splicing

<p>This section provides links to proteins that are similar to the protein sequence(s) described in this entry at different levels of sequence identity thresholds (100%, 90% and 50%) based on their membership in UniProt Reference Clusters (<a href="">UniRef</a>).<p><a href='/help/similar_proteins_section' target='_top'>More...</a></p>Similar proteinsi

<p>This section is used to point to information related to entries and found in data collections other than UniProtKB.<p><a href='/help/cross_references_section' target='_top'>More...</a></p>Cross-referencesi

Sequence databases

Select the link destinations:
Links Updated
X08091 Genomic RNA Translation: CAA30889.1

3D structure databases


Family and domain databases

HAMAPiMF_04069, INFV_M2, 1 hit
InterProiView protein in InterPro
IPR002089, Flu_M2
PfamiView protein in Pfam
PF00599, Flu_M2, 1 hit

ProtoNet; Automatic hierarchical classification of proteins


MobiDB: a database of protein disorder and mobility annotations


<p>This section provides general information on the entry.<p><a href='/help/entry_information_section' target='_top'>More...</a></p>Entry informationi

<p>This subsection of the 'Entry information' section provides a mnemonic identifier for a UniProtKB entry, but it is not a stable identifier. Each reviewed entry is assigned a unique entry name upon integration into UniProtKB/Swiss-Prot.<p><a href='/help/entry_name' target='_top'>More...</a></p>Entry nameiM2_I50A0
<p>This subsection of the 'Entry information' section provides one or more accession number(s). These are stable identifiers and should be used to cite UniProtKB entries. Upon integration into UniProtKB, each entry is assigned a unique accession number, which is called 'Primary (citable) accession number'.<p><a href='/help/accession_numbers' target='_top'>More...</a></p>AccessioniPrimary (citable) accession number: P10921
<p>This subsection of the 'Entry information' section shows the date of integration of the entry into UniProtKB, the date of the last sequence update and the date of the last annotation modification ('Last modified'). The version number for both the entry and the <a href="">canonical sequence</a> are also displayed.<p><a href='/help/entry_history' target='_top'>More...</a></p>Entry historyiIntegrated into UniProtKB/Swiss-Prot: July 1, 1989
Last sequence update: July 1, 1989
Last modified: October 7, 2020
This is version 111 of the entry and version 1 of the sequence. See complete history.
<p>This subsection of the 'Entry information' section indicates whether the entry has been manually annotated and reviewed by UniProtKB curators or not, in other words, if the entry belongs to the Swiss-Prot section of UniProtKB (<strong>reviewed</strong>) or to the computer-annotated TrEMBL section (<strong>unreviewed</strong>).<p><a href='/help/entry_status' target='_top'>More...</a></p>Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programViral Protein Annotation Program

<p>This section contains any relevant information that doesn't fit in any other defined sections<p><a href='/help/miscellaneous_section' target='_top'>More...</a></p>Miscellaneousi


  1. SIMILARITY comments
    Index of protein domains and families
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