9.A.10 The Oligomeric Probable Pore-forming SpoIIA Toxin (SpoIIA) Family SpoIISAB is a toxin-antitoxin module encoded on the chromosomes of Bacillus subtilis and related Bacilli. The SpoIISA toxin targets the cytoplasmic membrane and induces lysis in both B. subtilis and E. coli. However, the precise manner of SpoIISA toxicity is unknown. The N-terminal, transmembrane domain of SpoIISA has three verified TMSs while the C-terminal half of the protein is hydrophilic and localized to the cytoplasmic side of the membrane (Makroczyova J et al, 2014; PMID 25039482). Using truncated SpoIISA constructs, Makroczyova et al (2014) showed that the entire transmembrane domain is required for toxicity. The evidence is consistent with the proposal that the oligomerization of this transmembrane domain is crucial for the activity of SpoIISA, possibly by forming a pore-like structure.
Examples:
TC#	Name	Organismal Type	Example
9.A.10.1.1	The SpoIISA oligomeric toxin with 3 N-terminal TMSs and a C-terminal hydrophilic domain. The oligomeric structure probably forms a pore in the membrane. The anti-toxin, SpoIISB (56 aas; O34800) forms an A₂B₂ heterotetramer (Makroczyova J et al, 2014; PMID 25039482).	Firmicites	SpoIIA toxin of Bacillus subtilis

9.A.10.1.2	SpoIIA homologue of 245 aas and 3 TMSs	Firmicutes	SpoIIA homologue of Bacillus cereus

Examples:
TC#	Name	Organismal Type	Example
9.A.10.2.1	Uncharacterized protein of 314 aas and 4 N-terminal TMSs followed by a large hydrophilic domain.	Firmicutes	UP of Clostridium pasteurianum

9.A.10.2.2	Uncharacterized protein of 314 aas and 4 TMSs.	Firmicutes	UP of Clostridium straminisolvens

Examples:
TC#	Name	Organismal Type	Example
9.A.10.3.1	Uncharacterized protein of 189 aas and 6 TMSs	Spirochaetes	UP of Borrelia turicatae