Typically, a TA locus consists of a pair of genes: one encodes a stable toxin that inhibits essential cellular functions, and another encodes a labile antitoxin that neutralizes the activity of its cognate toxin. The known TA loci can be classified into 8 types based on the nature and mode of action of the antitoxins, namely types I to VIII described in the review by Dukas Jurėnas et al. (2022). The majority of described toxins are proteins (types I to VII), while the toxins are RNAs for type VIII TA pairs. Antitoxins are proteins for types II and IV to VII TA pairs but are RNAs in types I, III and VIII TA pairs.

• TA families

• Type I 28
• Type II 91
• Type III 4
• Type IV 8
• Type V 1
• Type VI 1
• Type VII 2
• Type VIII 2

TA family	Toxin	Antitoxin	Toxin target	Number of Exp. TA loci
bsrG-as-bsrG	bsrG	as-bsrG	cell wall synthesis	1
txpA-ratA	txpA	ratA	cell membrane and cell wall synthesis	8
yonT-SR6	yonT	SR6		1
tisB-istR	tisB	istR	ATP synthesis	2
symER	symE	symR	mRNA cleavage (Translation)	2
ibs-sib	ibs	sib		5
shoB-ohsC	shoB	ohsC	membrane depolarization and stress response	2
ralRA	ralR	ralA	DNA polymerase	3
sprG-sprF	SprG	SprF		8
ldrD-rdlD	ldrD	rdlD	ATP synthesis and stress response	24

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The number of experimentally validated TA loci