P13423 · PAG_BACAN

  • Protein
    Protective antigen
  • Gene
    pagA
  • Status
    UniProtKB reviewed (Swiss-Prot)
  • Amino acids
  • Protein existence
    Evidence at protein level
  • Annotation score
    5/5

Function

function

Protective antigen constitutes one of the three proteins composing the anthrax toxin; it mediates attachment to host cells and translocation of edema factor (EF) and lethal factor (LF) into the host cytoplasm (PubMed:11700562, PubMed:14507921, PubMed:15243628, PubMed:15326297).
PA associated with LF forms the lethal toxin (LeTx) and causes death when injected; PA associated with EF forms the edema toxin (EdTx) and produces edema (PubMed:1651334).
PA induces immunity to infection with anthrax (PubMed:11544370).

Protective antigen

Mediates the attachment to host cells by binding host cell receptors ANTXR1 and ANTXR2 (PubMed:11700562, PubMed:14507921, PubMed:15243628, PubMed:15326297).
Following host cell surface attachment, PA is cleaved by FURIN to generate the PA-63 (Protective antigen PA-63) form, which constitutes the mature form of the protein that oligomerizes and forms a pore to translocate the enzymatic toxin components edema factor (EF) and lethal factor (LF) into the host cytosol (PubMed:11700562, PubMed:15243628, PubMed:15326297).

Protective antigen PA-63

Mature form that oligomerizes and forms a pore to translocate the enzymatic toxin components edema factor (EF) and lethal factor (LF) into the host cytosol (PubMed:15243628, PubMed:15326297).
Following attachment to host cell receptors and cleavage by FURIN, homooligomerizes to form ring-shaped oligomers that are in a pre-pore conformation, and associates with EF and LF (PubMed:10085027, PubMed:12117959, PubMed:15313199).
Toxin-leaded complexes are then endocytosed in a clathrin-dependent process, followed by a conformational change of oligomerized PA-63 from the pre-pore to pore state, which is triggered by the low pH in the endosome (PubMed:10085027, PubMed:12551953, PubMed:15326297, PubMed:20221438).
Once active, the pore mediates unfolding of EF and LF, which pass through the pore and translocate into the host cytosol (PubMed:16051798, PubMed:21037566, PubMed:32047164, PubMed:32521227, PubMed:32810181).

Features

Showing features for site, binding site.

TypeIDPosition(s)Description
Site196-197Cleavage; by FURIN
Binding site206Ca2+ 1 (UniProtKB | ChEBI)
Site207Alpha-clamp
Binding site208Ca2+ 1 (UniProtKB | ChEBI)
Binding site208Ca2+ 2 (UniProtKB | ChEBI)
Binding site210Ca2+ 1 (UniProtKB | ChEBI)
Binding site210Ca2+ 2 (UniProtKB | ChEBI)
Binding site212Ca2+ 1 (UniProtKB | ChEBI)
Site216Alpha-clamp
Binding site217Ca2+ 1 (UniProtKB | ChEBI)
Binding site217Ca2+ 2 (UniProtKB | ChEBI)
Binding site251Ca2+ 2 (UniProtKB | ChEBI)
Binding site254Ca2+ 2 (UniProtKB | ChEBI)
Binding site264Ca2+ 2 (UniProtKB | ChEBI)
Site265Alpha-clamp
Site343-344Cleavage; by chymotrypsin; required for translocation of LF and EF
Site456Phi-clamp
Site493Alpha-clamp
Site712Essential for binding to cell receptor

GO annotations

AspectTerm
Cellular Componentextracellular region
Cellular Componenthost cell cytosol
Cellular Componenthost cell endosome membrane
Cellular Componenthost cell plasma membrane
Cellular Componentmembrane
Molecular Functionidentical protein binding
Molecular Functionmetal ion binding
Molecular Functiontoxin activity
Biological Processnegative regulation of MAPK cascade
Biological Processpositive regulation of apoptotic process in another organism
Biological Processprotein homooligomerization

Keywords

Enzyme and pathway databases

Protein family/group databases

    • 1.C.42.1.1the channel-forming bacillus anthracis protective antigen (bapa) family

Names & Taxonomy

Protein names

  • Recommended name
    Protective antigen
  • Short names
    PA
  • Alternative names
    • Anthrax toxins translocating protein
    • PA-83
      (PA83
      )
  • Cleaved into 2 chains

Gene names

    • Name
      pagA
    • Synonyms
      pag
    • Ordered locus names
      pXO1-110, BXA0164, GBAA_pXO1_0164

Encoded on

  • Plasmid pXO1

Organism names

  • Taxonomic identifier
  • Strains
    • 28
    • 33
    • BA1024
    • BA1035
    • V770-NP1-R / ATCC 14185
  • Taxonomic lineage
    Bacteria > Bacillota > Bacilli > Bacillales > Bacillaceae > Bacillus > Bacillus cereus group

Accessions

  • Primary accession
    P13423
  • Secondary accessions
    • Q937W2
    • Q937W3
    • Q9F5R7
    • Q9KH69
    • Q9RQU2

Proteomes

Subcellular Location

Protective antigen

Secreted
Host cell membrane
Note: Secreted through the Sec-dependent secretion pathway (PubMed:12606539).
Therefore, PA is translocated across the membrane in an unfolded state and then it is folded into its native configuration on the trans side of the membrane, prior to its release to the environment (PubMed:12606539).
PA requires the extracellular chaperone PrsA for efficient folding (PubMed:12606539).
It circulates in the host blood and binds host cell receptors at the cell surface (PubMed:11700562, PubMed:14507921).

Protective antigen PA-63

Host cell membrane
; Multi-pass membrane protein
Host endosome membrane
; Multi-pass membrane protein
Note: Following attachment to host cell receptors at the cell surface and cleavage by FURIN, homooligomerizes to form ring-shaped oligomers that are in a pre-pore conformation, and associates with EF and LF (PubMed:15313199).
Loaded complexes are then endocytosed in a clathrin-dependent process, followed by a conformational change of oligomerized PA-63 from the pre-pore to pore state, which is triggered by the low pH in the endosome (PubMed:10085027, PubMed:15326297).

Features

Showing features for transmembrane.

TypeIDPosition(s)Description
Transmembrane331-342Beta stranded
Transmembrane345-354Beta stranded

Keywords

Phenotypes & Variants

Features

Showing features for mutagenesis, natural variant.

TypeIDPosition(s)Description
Mutagenesis193Reduced cleavage by FURIN and reduced toxin activity.
Mutagenesis193-196Abolished cleavage by FURIN and abolished toxin activity.
Mutagenesis194-195Does not affect cleavage by FURIN and does not affect toxin activity.
Mutagenesis194-196Abolished cleavage by FURIN and abolished toxin activity.
Mutagenesis207Abolished interaction with LF.
Mutagenesis213Decrease in the ability to bind to LF and partially toxic at high concentrations.
Mutagenesis216Decrease in the ability to bind to LF and partially toxic at high concentrations.
Mutagenesis229Abolished interaction with LF.
Mutagenesis231Loss of ability to bind to LF and completely non-toxic.
Mutagenesis231Does not affect significantly interaction with LF, while it impairs tranlocation of LF.
Mutagenesis232Loss of ability to bind to LF and completely non-toxic.
Mutagenesis234Loss of ability to bind to LF and completely non-toxic.
Mutagenesis234Does not affect significantly interaction with LF.
Mutagenesis236Loss of ability to bind to LF and completely non-toxic.
Mutagenesis236Abolished interaction with LF.
Mutagenesis239Decrease in the ability to bind to LF and partially toxic at high concentrations.
Mutagenesis240Abolished interaction with LF.
Mutagenesis255No effect on LF-binding ability and as toxic as the wild-type.
Mutagenesis265No effect on LF-binding ability and as toxic as the wild-type.
Mutagenesis265Impaired translocation of LF.
Mutagenesis289Reduced toxicity in combination with lethal factor. Decreased membrane insertion and translocation of LF.
Natural variant295in strain: PAI
Mutagenesis342Loss of toxicity probably due to loss of capability to translocate LF.
Mutagenesis342-343Loss of toxicity probably due to loss of capability to translocate LF.
Mutagenesis342-344Decrease in toxicity probably due to slow translocation of LF.
Mutagenesis344Decrease in toxicity probably due to slow translocation of LF.
Mutagenesis375Loss of toxicity probably due to faulty membrane insertion or translocation of LF/EF into the cytosol.
Mutagenesis379No effect.
Mutagenesis381Loss of toxicity probably due to faulty membrane insertion or translocation of LF/EF into the cytosol.
Natural variant392in strain: PAI
Mutagenesis393Loss of capability to undergo conformational changes that lead to pore formation and translocation.
Mutagenesis409Loss of capability to undergo conformational changes that lead to pore formation and translocation.
Mutagenesis411Loss of capability to undergo conformational changes that lead to pore formation and translocation.
Mutagenesis422Loss of capability to undergo conformational changes that lead to pore formation and translocation.
Mutagenesis426Loss of capability to undergo conformational changes that lead to pore formation and translocation.
Mutagenesis428Loss of capability to undergo conformational changes that lead to pore formation and translocation.
Mutagenesis440Loss of capability to undergo conformational changes that lead to pore formation and translocation.
Mutagenesis451Loss of capability to undergo conformational changes that lead to pore formation and translocation.
Mutagenesis454Loss of capability to undergo conformational changes that lead to pore formation and translocation.
Mutagenesis456Loss of capability to undergo conformational changes that lead to pore formation and translocation.
Mutagenesis456Abolished ability for mediate LF and EF protein translocation.
Mutagenesis512Loss of heptamerization capability.
Mutagenesis541Loss of heptamerization capability.
Mutagenesis543Decrease in heptamerization capability.
Natural variant560in Sverdlovsk sample
Natural variant565in strain: BA1024
Mutagenesis581Loss of toxicity due to defective oligomerization.
Mutagenesis583Decrease in toxicity due to defective oligomerization.
Mutagenesis591Loss of toxicity due to defective oligomerization.
Mutagenesis595Loss of toxicity due to defective oligomerization.
Natural variant600in strain: BA1024, V770-NP1-R, Carbosap and Ferrara
Mutagenesis603Loss of toxicity due to defective oligomerization.
Mutagenesis621No effect.
Mutagenesis686Decrease in toxicity due to decrease in cell binding.
Mutagenesis708No effect on toxicity.
Mutagenesis709Slight decrease in toxicity.
Mutagenesis710Great decrease in toxicity due to decrease in cell binding.
Mutagenesis711Loss of toxicity due to decrease in cell binding.
Mutagenesis712Loss of toxicity due to decrease in cell binding.
Mutagenesis713No effect on toxicity.
Mutagenesis714No effect on toxicity.
Mutagenesis715Great decrease in toxicity due to decrease in cell binding.
Mutagenesis716Decrease in toxicity due to decrease in cell binding.
Mutagenesis717No effect on toxicity.
Mutagenesis718Decrease in toxicity due to decrease in cell binding.
Mutagenesis719No effect on toxicity.
Mutagenesis720No effect on toxicity.
Mutagenesis721No effect on toxicity.
Mutagenesis722No effect on toxicity.

Variants

We now provide the "Disease & Variants" viewer in its own tab.

The viewer provides 5 variants from UniProt as well as other sources including ClinVar and dbSNP.

Go to variant viewer

Miscellaneous

Chemistry

PTM/Processing

Features

Showing features for signal, chain.

TypeIDPosition(s)Description
Signal1-29
ChainPRO_000002199730-196Protective antigen PA-20
ChainPRO_000002199630-764Protective antigen
ChainPRO_0000021998197-764Protective antigen PA-63

Post-translational modification

Proteolytic activation by FURIN cleaves the protein in two parts, PA-20 and PA-63; the latter is the mature protein (PubMed:11207581, PubMed:1438214, PubMed:1644824, PubMed:8051159).
The cleavage occurs at the cell surface and probably in the serum of infected animals as well; both native and cleaved PA are able to bind to the cell receptor (PubMed:11207581, PubMed:8051159).
The release of PA-20 from the remaining receptor-bound PA-63 exposes the binding site for EF and LF, and promotes oligomerization and internalization of the protein (PubMed:11207581, PubMed:8051159).

Keywords

Interaction

Subunit

Protective antigen

Interacts with host ANTXR1 and ANTXR2.

Protective antigen PA-63

Homooligomer; homooligomerizes to form homoheptamers (PA-637) or homooctamers (PA-638) (PubMed:10085027, PubMed:16051798, PubMed:19627991, PubMed:20433851, PubMed:25778700, PubMed:32810181).
PA-637 or PA-638 form ring-shaped oligomers that are in a pre-pore conformation, which do not penetrate the host membrane (PubMed:19627991, PubMed:20433851, PubMed:32810181).
PA-638 displays an enhanced stability, suggesting that this form circulates in the blood to reach and exert toxicity even in distant tissues (PubMed:20433851).
Interacts with lethal factor (LF) and edema factor (EF); can bind LF and EF simultaneously and interaction takes place following homooligomerization on the host cell membrane (PubMed:10085027, PubMed:12117959, PubMed:15313199, PubMed:21037566, PubMed:32047164, PubMed:32521227, PubMed:32810181).
PA-637 homoheptamer interacts with three molecules of LF to form the PA7LF3 complex, in which the relative position of the N-terminal alpha-helices in the three LFs determines which factor is translocated first (PubMed:32810181).

Binary interactions

Protein-protein interaction databases

Chemistry

Family & Domains

Features

Showing features for region, domain, compositional bias.

TypeIDPosition(s)Description
Region30-287Domain 1, calcium-binding; LF and EF binding sites
Domain43-179PA14
Region176-214Disordered
Region231-239Alpha-clamp
Region288-516Domain 2, membrane insertion and heptamerization
Compositional bias302-331Polar residues
Region302-333Disordered
Region517-624Domain 3, heptamerization
Region625-764Domain 4, binding to the receptor

Domain

The molecule is folded into four functional domains (PubMed:1651334, PubMed:9039918).
Each domain is required for a particular step in the toxicity process (PubMed:1651334).
Domain 1 contains two calcium ions and the proteolytic activation site (PubMed:1651334).
Cleavage of the PA monomer releases the subdomain 1a, which is the N-terminal fragment of 20-kDa (PA-20) (PubMed:11207581, PubMed:8051159, PubMed:9039918).
The subdomain 1b is part of the remaining 63-kDa fragment (PA-63) and contains the binding sites for LP and EF (PubMed:11207581, PubMed:8051159, PubMed:9039918).
Domain 2 is a beta-barrel core containing a large flexible loop that has been implicated in membrane insertion and pore formation (PubMed:11356563, PubMed:1651334, PubMed:9039918).
There is a chymotrypsin cleavage site in this loop that is required for toxicity (PubMed:1512256, PubMed:7961869, PubMed:9039918).
Domain 3 has a hydrophobic patch thought to be involved in protein-protein interactions (PubMed:11222612, PubMed:1651334, PubMed:9039918).
Domain 4 appears to be a separate domain and shows limited contact with the other three domains: it would swing out of the way during membrane insertion (PubMed:10085028, PubMed:12771151, PubMed:1651334, PubMed:9039918).
It is required for binding to the receptor; the small loop is involved in receptor recognition (PubMed:10085028, PubMed:12771151, PubMed:1651334, PubMed:9039918).

Protective antigen PA-63

Phe-456 residue forms the phi-clamp in the pore and catalyzes protein translocation via a charge-state-dependent Brownian ratchet (PubMed:16051798, PubMed:25778700).
During conversion of the heptameric pre-pore precursor to the pore, the seven Phe-427 residues converge within the lumen to generate the narrowest point in the channel lumen (6 Angstroms in width) (PubMed:16051798, PubMed:25778700).
To pass through this hydrophobic restriction, substrate proteins LF and EF need to be unfolded prior to translocation (PubMed:25778700).

Protective antigen PA-63

The alpha-clamp consists in an amphipathic cleft between two adjacent PA protomers, which assists the unfolding of substrate proteins LF and EF (PubMed:21037566, PubMed:32047164, PubMed:32521227).
The alpha-clamp binds non-specifically to alpha-helices of substrate proteins LF and EF (PubMed:21037566, PubMed:32047164, PubMed:32521227).

Sequence similarities

Belongs to the bacterial binary toxin family.

Keywords

Phylogenomic databases

Family and domain databases

Sequence

  • Sequence status
    Complete
  • Sequence processing
    The displayed sequence is further processed into a mature form.
  • Length
    764
  • Mass (Da)
    85,811
  • Last updated
    2001-10-18 v2
  • Checksum
    3AE1EFBF48FAA03F
MKKRKVLIPLMALSTILVSSTGNLEVIQAEVKQENRLLNESESSSQGLLGYYFSDLNFQAPMVVTSSTTGDLSIPSSELENIPSENQYFQSAIWSGFIKVKKSDEYTFATSADNHVTMWVDDQEVINKASNSNKIRLEKGRLYQIKIQYQRENPTEKGLDFKLYWTDSQNKKEVISSDNLQLPELKQKSSNSRKKRSTSAGPTVPDRDNDGIPDSLEVEGYTVDVKNKRTFLSPWISNIHEKKGLTKYKSSPEKWSTASDPYSDFEKVTGRIDKNVSPEARHPLVAAYPIVHVDMENIILSKNEDQSTQNTDSQTRTISKNTSTSRTHTSEVHGNAEVHASFFDIGGSVSAGFSNSNSSTVAIDHSLSLAGERTWAETMGLNTADTARLNANIRYVNTGTAPIYNVLPTTSLVLGKNQTLATIKAKENQLSQILAPNNYYPSKNLAPIALNAQDDFSSTPITMNYNQFLELEKTKQLRLDTDQVYGNIATYNFENGRVRVDTGSNWSEVLPQIQETTARIIFNGKDLNLVERRIAAVNPSDPLETTKPDMTLKEALKIAFGFNEPNGNLQYQGKDITEFDFNFDQQTSQNIKNQLAELNATNIYTVLDKIKLNAKMNILIRDKRFHYDRNNIAVGADESVVKEAHREVINSSTEGLLLNIDKDIRKILSGYIVEIEDTEGLKEVINDRYDMLNISSLRQDGKTFIDFKKYNDKLPLYISNPNYKVNVYAVTKENTIINPSENGDTSTNGIKKILIFSKKGYEIG

Features

Showing features for compositional bias, sequence conflict.

TypeIDPosition(s)Description
Compositional bias302-331Polar residues
Sequence conflict314in Ref. 1; AAA22637

Keywords

Sequence databases

Nucleotide SequenceProtein SequenceMolecule TypeStatus
M22589
EMBL· GenBank· DDBJ
AAA22637.1
EMBL· GenBank· DDBJ
Genomic DNA
AF306778
EMBL· GenBank· DDBJ
AAG24446.1
EMBL· GenBank· DDBJ
Genomic DNA
AF306779
EMBL· GenBank· DDBJ
AAG24447.1
EMBL· GenBank· DDBJ
Genomic DNA
AF306780
EMBL· GenBank· DDBJ
AAG24448.1
EMBL· GenBank· DDBJ
Genomic DNA
AF306781
EMBL· GenBank· DDBJ
AAG24449.1
EMBL· GenBank· DDBJ
Genomic DNA
AF306782
EMBL· GenBank· DDBJ
AAG24450.1
EMBL· GenBank· DDBJ
Genomic DNA
AF306783
EMBL· GenBank· DDBJ
AAG24451.1
EMBL· GenBank· DDBJ
Genomic DNA
AF268967
EMBL· GenBank· DDBJ
AAF86457.1
EMBL· GenBank· DDBJ
Genomic DNA
AF065404
EMBL· GenBank· DDBJ
AAD32414.1
EMBL· GenBank· DDBJ
Genomic DNA
AE011190
EMBL· GenBank· DDBJ
AAM26109.1
EMBL· GenBank· DDBJ
Genomic DNA
AE017336
EMBL· GenBank· DDBJ
AAT28905.2
EMBL· GenBank· DDBJ
Genomic DNA
AJ413936
EMBL· GenBank· DDBJ
CAC93934.1
EMBL· GenBank· DDBJ
Genomic DNA
AJ413937
EMBL· GenBank· DDBJ
CAC93935.1
EMBL· GenBank· DDBJ
Genomic DNA
AB125961
EMBL· GenBank· DDBJ
BAD14937.1
EMBL· GenBank· DDBJ
Genomic DNA

Genome annotation databases

Similar Proteins

Disclaimer

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