A0A515MEN7 · ACTPB_ACTFR
- ProteinDELTA-actitoxin-Afr1c
- StatusUniProtKB reviewed (Swiss-Prot)
- Amino acids179 (go to sequence)
- Protein existenceEvidence at protein level
- Annotation score4/5
Function
function
Pore-forming toxin (PFT) that consists of a crown-shaped octamer or nonamer that forms cation-selective hydrophilic pores of about 1.5 nm (inside) and 13 nm (outside) and causes cytolysis (By similarity).
It causes cardiac stimulation (By similarity).
Also causes hemolysis (HC50=0.3 nM) (PubMed:31295915).
Interestingly, the Phe-16 is crucial for hemolysis (By similarity).
Pore formation is a multi-step process that involves specific recognition of membrane sphingomyelin (but neither cholesterol nor phosphatidylcholine) using aromatic rich region and adjacent phosphocholine (POC) binding site, firm binding to the membrane (mainly driven by hydrophobic interactions) accompanied by the transfer of the N-terminal region to the lipid-water interface and finally pore formation after oligomerization of monomers (By similarity).
It is probable that a dimeric form is an assembly intermediate before the complete oligomerization (By similarity).
The formation of stable pores occurs only in vesicles composed of DOPC/SM (there is no oligomerization when the PFT is treated with vesicles of DOPC or SM alone) (By similarity).
The transmembrane pore displays 8 lateral perforations, one at each subunit-subunit interface, partially occupied by the acyl-chain region of a bridging lipid (By similarity).
Each pore contains 24 lipid molecules, firmly bound to each subunit, that is, 3 lipids (L1, L2, L3, L4 and/or L5) are associated to each subunit (By similarity).
Lipid L1 bridges 2 subunits, whereas lipids L2 and L3 bind to sites at single subunit (By similarity).
It causes cardiac stimulation (By similarity).
Also causes hemolysis (HC50=0.3 nM) (PubMed:31295915).
Interestingly, the Phe-16 is crucial for hemolysis (By similarity).
Pore formation is a multi-step process that involves specific recognition of membrane sphingomyelin (but neither cholesterol nor phosphatidylcholine) using aromatic rich region and adjacent phosphocholine (POC) binding site, firm binding to the membrane (mainly driven by hydrophobic interactions) accompanied by the transfer of the N-terminal region to the lipid-water interface and finally pore formation after oligomerization of monomers (By similarity).
It is probable that a dimeric form is an assembly intermediate before the complete oligomerization (By similarity).
The formation of stable pores occurs only in vesicles composed of DOPC/SM (there is no oligomerization when the PFT is treated with vesicles of DOPC or SM alone) (By similarity).
The transmembrane pore displays 8 lateral perforations, one at each subunit-subunit interface, partially occupied by the acyl-chain region of a bridging lipid (By similarity).
Each pore contains 24 lipid molecules, firmly bound to each subunit, that is, 3 lipids (L1, L2, L3, L4 and/or L5) are associated to each subunit (By similarity).
Lipid L1 bridges 2 subunits, whereas lipids L2 and L3 bind to sites at single subunit (By similarity).
Miscellaneous
This protein has been found to bind carbohydrates, since it shows a substantial delay in elution profile in size-exclusion chromatography. The carbohydrate pocket ovelaps with the lipid-binding module of actinoporins.
Temperature Dependence
Stable up to about 62 degrees Celsius.
Features
Showing features for site, binding site.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Site | 16 | Part of the hydrophobic cavity (in subunit A) that receives Val-60 from the adjacent subunit (B); essential in hemolysis, since it is critical for pore formation in cholesterol-rich membrane cells (such as red blood cells) | ||||
Sequence: F | ||||||
Binding site | 31 | an N-(acyl)-sphingosylphosphocholine 1 (UniProtKB | ChEBI); bridging lipid L1; in subunit A; in oligomeric forms only | ||||
Sequence: R | ||||||
Binding site | 51 | N-acetyl-D-glucosamine 6-sulfate (UniProtKB | ChEBI) | ||||
Sequence: Y | ||||||
Binding site | 53 | an N-(acyl)-sphingosylphosphocholine 2 (UniProtKB | ChEBI); lipid L2; in monomeric and oligomeric forms | ||||
Sequence: R | ||||||
Binding site | 53 | N-acetyl-D-glucosamine 6-sulfate (UniProtKB | ChEBI) | ||||
Sequence: R | ||||||
Binding site | 54 | an N-(acyl)-sphingosylphosphocholine 2 (UniProtKB | ChEBI); lipid L2; in monomeric and oligomeric forms | ||||
Sequence: S | ||||||
Binding site | 79 | an N-(acyl)-sphingosylphosphocholine 1 (UniProtKB | ChEBI); bridging lipid L1; in subunit B; in oligomeric forms only | ||||
Sequence: R | ||||||
Binding site | 85 | an N-(acyl)-sphingosylphosphocholine 2 (UniProtKB | ChEBI); lipid L2; in monomeric and oligomeric forms | ||||
Sequence: G | ||||||
Binding site | 113 | an N-(acyl)-sphingosylphosphocholine 2 (UniProtKB | ChEBI); lipid L2; in monomeric and oligomeric forms | ||||
Sequence: Y | ||||||
Binding site | 114 | an N-(acyl)-sphingosylphosphocholine 5 (UniProtKB | ChEBI); lipid L5; in monomeric and oligomeric forms | ||||
Sequence: S | ||||||
Binding site | 116 | an N-(acyl)-sphingosylphosphocholine 3 (UniProtKB | ChEBI); lipid L3; in monomeric and oligomeric forms | ||||
Sequence: W | ||||||
Binding site | 133 | an N-(acyl)-sphingosylphosphocholine 4 (UniProtKB | ChEBI); lipid L4; in monomeric and oligomeric forms | ||||
Sequence: Y | ||||||
Binding site | 137 | an N-(acyl)-sphingosylphosphocholine 3 (UniProtKB | ChEBI); lipid L3; in monomeric and oligomeric forms | ||||
Sequence: Y | ||||||
Binding site | 138 | an N-(acyl)-sphingosylphosphocholine 4 (UniProtKB | ChEBI); lipid L4; in monomeric and oligomeric forms | ||||
Sequence: Y | ||||||
Binding site | 138 | N-acetyl-D-glucosamine 6-sulfate (UniProtKB | ChEBI) | ||||
Sequence: Y | ||||||
Binding site | 144 | an N-(acyl)-sphingosylphosphocholine 5 (UniProtKB | ChEBI); lipid L5; in monomeric and oligomeric forms | ||||
Sequence: R | ||||||
Site | 149 | Part of the hydrophobic cavity (in subunit A) that receives Val-60 from the adjacent subunit (B) | ||||
Sequence: W | ||||||
Site | 163 | Part of the hydrophobic cavity (in subunit A) that receives Val-60 from the adjacent subunit (B) | ||||
Sequence: F | ||||||
Binding site | 168 | an N-(acyl)-sphingosylphosphocholine 1 (UniProtKB | ChEBI); bridging lipid L1; in subunit A; in oligomeric forms only | ||||
Sequence: G |
GO annotations
Aspect | Term | |
---|---|---|
Cellular Component | extracellular region | |
Cellular Component | nematocyst | |
Cellular Component | other organism cell membrane | |
Cellular Component | pore complex | |
Molecular Function | channel activity | |
Molecular Function | lipid binding | |
Molecular Function | toxin activity | |
Biological Process | cytolysis in another organism | |
Biological Process | monoatomic cation transport | |
Biological Process | pore complex assembly |
Keywords
- Molecular function
- Biological process
- Ligand
Names & Taxonomy
Protein names
- Recommended nameDELTA-actitoxin-Afr1c
- Short namesDELTA-AITX-Afr1c
- Alternative names
Organism names
- Taxonomic lineageEukaryota > Metazoa > Cnidaria > Anthozoa > Hexacorallia > Actiniaria > Actiniidae > Actinia
Accessions
- Primary accessionA0A515MEN7
Subcellular Location
UniProt Annotation
GO Annotation
Note: Forms an alpha-helical membrane channel in the prey.
Keywords
- Cellular component
PTM/Processing
Features
Showing features for chain.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Chain | PRO_0000453823 | 1-179 | DELTA-actitoxin-Afr1c | |||
Sequence: SAEVAGAIIDGASLTFDVLQTVLKALGDVSRKIAVGIDNEPGMTWTAMNTYFRSGTSDVILPHTVPHSKALLYDGQKNRGPVTTGVVGVIAYAMSDGNTLAVLFSIPFDYNLYSNWWNVKVYKGHRRADQAMYEELYYDFSPFRGDNGWHTKSIGYGLKGRGFMNSSGKAILQIHVNKV |
Interaction
Subunit
Octamer or nonamer in membranes. Monomer in the soluble state.
Structure
Family & Domains
Features
Showing features for region, motif.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Region | 1-29 | N-terminal alpha-helix that contributes to the pore | ||||
Sequence: SAEVAGAIIDGASLTFDVLQTVLKALGDV | ||||||
Region | 11-30 | N-terminal region | ||||
Sequence: GASLTFDVLQTVLKALGDVS | ||||||
Region | 105-120 | Trp-rich region, which is important for the binding to lipid membrane | ||||
Sequence: SIPFDYNLYSNWWNVK | ||||||
Motif | 144-146 | Cell attachment site, crucial for protein stability | ||||
Sequence: RGD |
Domain
Composed of a long N-terminal alpha-helix and a core region rich in beta-sheet structures. Before the pore formation, the alpha-helix binds the lipid membrane, partitions into the lipid-water interface and stabilizes the monomeric molecule on the membrane. Finally, it traverses the bilayer, thus forming the transmembrane pore.
Sequence similarities
Belongs to the actinoporin family. Sea anemone subfamily.
Keywords
- Domain
Family and domain databases
Sequence
- Sequence statusComplete
- Length179
- Mass (Da)19,672
- Last updated2021-09-29 v2
- ChecksumBA2341AA9D3E5FF5
Mass Spectrometry
Keywords
- Technical term