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1.C.38.1.8
Fragaceatoxin C (FraC) of the strawberry anemone (Structure solved to 1.8 Å resolution; It is a crown-shaped nonamer with an external diameter of about 11.0 nm and an internal diameter of approximately 5.0 nm.) Almost identical to Equinatoxin II (1.C.38.1.1) (Mechaly et al., 2011).  Fragaceatoxin C (FraC) is an α-barrel pore-forming toxin (PFT). The crystal structures of FraC at four different stages of the lytic mechanism have been determined at 3.1Å resolution, namely the water-soluble state, the monomeric lipid-bound form, an assembly intermediate and the fully assembled transmembrane pore (Tanaka et al. 2015). The structure of the transmembrane pore exhibits a unique architecture composed of both protein and lipids, with some of the lipids lining the pore wall, acting as assembly cofactors. The pore exhibits lateral fenestrations that expose the hydrophobic core of the membrane to the aqueous environment. The incorporation of lipids from the target membrane within the structure of the pore provides a membrane-specific trigger for the activation of this haemolytic toxin.  It has been reconstituted in  planar lipid bilayers and engineered for DNA analysis.  It shows a funnel-shaped geometry that allows tight wrapping around single-stranded DNA (ssDNA), resolving between homopolymeric C, T, and A polynucleotide stretches (Wloka et al. 2016). Despite the 1.2 nm internal constriction in the FraC pore, double-stranded DNA (dsDNA) can translocate through the nanopore at high applied potentials, presumably through deformation of the alpha-helical transmembrane region. Therefore, FraC nanopores might be useful for DNA sequencing and dsDNA analysis. Pore formation goes through a dimer intermediate and then generates the active octamer. Disrupting the key hydrophobic interaction between V60 and F163 (FraC numbering scheme) in the oligomerization interface of FraC, equinatoxin II (EqtII) and sticholysin II (StII) impairs the pore formation activity (Mesa-Galloso et al. 2016).

Accession Number:B9W5G6
Protein Name:Fragaceatoxin C
Length:179
Molecular Weight:19719.00
Species:Actinia fragacea (Strawberry anemone) [396334]
Number of TMSs:1
Location1 / Topology2 / Orientation3: Secreted1
Substrate small molecules

Cross database links:

Pfam: PF06369   

Gene Ontology

GO:0042151 C:nematocyst
GO:0044218 C:other organism cell membrane
GO:0046930 C:pore complex
GO:0015267 F:channel activity
GO:0006812 P:cation transport
GO:0019835 P:cytolysis
GO:0052331 P:hemolysis in other organism involved in symbiotic interaction
GO:0009405 P:pathogenesis
GO:0046931 P:pore complex assembly

References (2)

[1] “Purification, cloning and characterization of fragaceatoxin C, a novel actinoporin from the sea anemone Actinia fragacea.”  Bellomio A.et.al.   19563820
[2] “Molecular mechanism of pore formation by actinoporins.”  Kristan K.C.et.al.   19268680
Structure:
3LIM   3VWI   3W9P   3ZWG   3ZWJ   4TSL   4TSN   4TSO   4TSP   4TSQ   [...more]

External Searches:

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  • 2° Structure (Network Protein Sequence Analysis)

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	SADVAGAVID GAGLGFDVLK TVLEALGNVK RKIAVGIDNE SGKTWTAMNT YFRSGTSDIV 
61:	LPHKVAHGKA LLYNGQKNRG PVATGVVGVI AYSMSDGNTL AVLFSVPYDY NWYSNWWNVR 
121:	VYKGQKRADQ RMYEELYYHR SPFRGDNGWH SRGLGYGLKS RGFMNSSGHA ILEIHVTKA