TCDB is operated by the Saier Lab Bioinformatics Group
TCIDNameDomainKingdom/PhylumProtein(s)
*1.C.4.1.1









Aerolysin (β-hemolysin; cytolytic enterotoxin) precursor (Parker et al., 1994).  Upon transition  from the prepore to pore, the aerolysin heptamer shows a unique concerted swirling movement, accompanied by a vertical collapse of the complex, ultimately leading to the insertion of a transmembrane beta-barrel (Degiacomi et al. 2013).  Multiple conformational states lead to rotation of the core lysin to unleash the membrane spanning regions (Whisstock and Dunstone 2013).  Monomer activation, dependent on proteolysis, is the rate-limiting step for pore formation (Bischofberger et al. 2016). Cryo-electron microscopy structures of three conformational intermediates and the final aerolysin pore provide insight into the conformational changes that allow pore formation. The structures reveal a protein fold consisting of two concentric beta-barrels, tightly kept together by hydrophobic interactions. This fold suggests a basis for the prion-like ultrastability of aerolysin pore and its stoichiometry (Iacovache et al. 2016).

Bacteria
Proteobacteria
Aerolysin precursor of Aeromonas hydrophila
*1.C.4.2.1









α-toxin forms large ion permeable (slightly anion-selective) pores with no lipid specificity. It induces rapid cell necrosis in many cell types (Knapp et al., 2009).

Bacteria
Firmicutes
α-toxin of Clostridium septicum (BAC54147)
*1.C.4.3.1









Enterolobin
Eukaryota
Viridiplantae
Enterolobin of Enterolobium contortisiliquum (A57982)
*1.C.4.4.1









Hydralysin (Sher et al., 2005; Zhang et al., 2003).  Hydrolysins comprise a family of pore-forming proteins that are secreted into the gastrovascular cavity during feeding, probably helping in disintegration of the prey (Sher and Zlotkin 2009). Induces an immediate fast muscle contraction followed by flaccid paralysis when injected into blowfly larvae. The paralytic effect is lower in mice and fish. Has strong cytolytic activity against insect Sf9 cells and human HeLa cells. Binds to erythrocyte membranes and has weak hemolytic activity by mediating oligomerization and pore formation (Zhang et al. 2003; Sher et al. 2008).

Eukaryota
Metazoa
Hydralysin of Hydra viridis (Q86LR2)
*1.C.4.4.2









Spherulin 2A

Eukaryota
Myxogastromycetidae
Spherulin 2A of Physarum polycephalum (P09352)
*1.C.4.4.3









Hemolytic lectin LSLc exhibits hemolytic and hemagglutinating activities. The structure at 2.6 Å resolution has been determined (Mancheño et al., 2005). The protein is hexameric. The monomer (35kDa) consists of two distinct modules: an N-terminal lectin module (a β-trefoil scaffold) and a pore-forming module (composed of domains 2 and 4) which resemble the β-pore-forming domains of aerolysin and ε-toxin (Mancheño et al., 2005).

Eukaryota
Fungi
LSLc of Laetiporus sulphureus (BAC78490)
*1.C.4.4.4









Parasporin-2 β-toxin (crystal structures are known) (Akiba et al., 2009; Akiba and Okumura 2016).

Bacteria
Firmicutes
Paraspora-2 of Bacillus thuringiensis (Q7WZI1)
*1.C.4.5.1









The pore forming toxin-like protein, Hfr-2
Eukaryota
Viridiplantae
Hfr-2 of Triticum aestivum (bread wheat) (AAW48295)
*1.C.4.5.2









Fhb1 protein (PFT gene product) of 478 aas with two agglutinin domains followed by a DON (ETX/MTX2) domain that has the toxin activity (Rawat et al. 2016).  Counteracts Fusarium head blight (FHB), caused by Fusarium graminearum, a devastating disease of wheat and barley.

Eukaryota
Viridiplantae
Fhb1 of Triticum aestivum
*1.C.4.6.1









Natterin-3 precursor (venom gland protein)
Eukaryota
Metazoa
Natterin-3 precursor of Thalassophryne nattereri (AAU11824)
*1.C.4.6.2









Natterin-like precursor of 315 aas from zebra fish

Eukaryota
Metazoa
Natterin-like protein of Danio rerio
*1.C.4.7.1









The Bin binary toxin, BinAB.  BinA is a toxic P42 protein (protein of 42 KDa) of 362 aas.  The 3-d structure of BinB (448 aas; 1.75 Å resolution) is available; it has two domains, an N-terminal sugar-binding lectin-like domain, and a C-terminal aerolysin-like β-barrel pore-forming domain. Although it shows low sequence identity with other members of the family, it is a member of the Aerolysin Family (Srisucharitpanit et al. 2014).  Protoxin subunits only form monomers, but in vitro activated toxin forms heterodimers. Maximal toxicity to mosquito larvae is achieved when the two subunits, BinA and BinB, are in a 1:1 molar ratio (Surya et al. 2016).

Bacteria
Firmicutes
BinAB of Lysinibacillus (Bacillus) sphaericus
BinA (P81935)
BinB (P10565)
*1.C.4.7.2









Cry35 of 385 aas.  Shares a common strucure with ε-toxin, ETX (Moar et al. 2016).

Bacteria
Firmicutes
Cry35 of Bacillus thuringiensis