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
yeeUV (cbtA-cbeA)	yeeV	yeeU		2
sdenTA	sdenT	sdenA		1
abiEi-abiEii	abiEi	abiEii		5
cptAB	cptA	cptB	FtsZ and MreB	2
FaRel-ATfaRel	faRel	ATfaRel		1
ygfYX	ygfX	ygfY		1
yafW-ykfI	ykfI	yafW	FtsZ and MreB (cell division and elongation)	1
yfjZ-ypjF	ypjF	yfjZ	FtsZ and MreB (cell division and elongation)	1

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The number of experimentally validated TA loci