Table 1.

Solved type II toxin-antitoxin structures grouped according to the DNA-binding domain of the antitoxins.

DNA-binding domain	Antitoxin	Toxin	Host organism	Toxin-antitoxin complex stoichiometries	References
HTH	HipB	HipA	Escherichia coli	HipB2HipA2	Schumacher et al., 2009
	HipBSO	HipASO	Shewanella oneidensis	(HipBSO)2(HipASO)2	Wen et al., 2014
	MqsA	MqsR	E. coli	MqsR-MqsA2-MqsR	Brown et al., 2009, 2011
	HigA	HigB	E. coli	unknowna	Arbing et al., 2010
	HigA	HigB	Proteus vulgaris	HigA2HigB2	Schureck et al., 2014
	HigA2	HigB2	Vibrio cholerae	Unknown	Hadži et al., 2013
	PezA	PezT	Streptococcus pneumoniae	PezA2PezT2	Khoo et al., 2007
RHH	RelB	RelE	E. coli	RelB2RelE2	Bøggild et al., 2012
	RelB	RelE	Methanococcus jannaschii	RelB2RelE2	Francuski and Saenger, 2009
	DinJ	YafQ	E. coli	DinJ2YafQ2	Liang et al., 2014; Ruangprasert et al., 2014
	ParD	ParE	E. coli plasmid RK2	ParD2b	Oberer et al., 2007
	ParD1	ParE1	Caulobacter crescentus	(ParD1)2(ParE1)2	Dalton and Crosson, 2010
	CcdA	CcdB	E. coli F plasmid	(CcdA37−72)(CcdB)2 (CcdA37−72)2(CcdB)2	Madl et al., 2006; De Jonge et al., 2009
	HicB3	HicA3	Yersinia pestis	(HicB3)4(HicA3)2	Bibi-Triki et al., 2014
	FitA	FitB	Neisseria gonorrhoeae	(FitA-FitB)4	Mattison et al., 2006
	VapB3	VapC3	Mycobacterium tuberculosis	(VapB3)2(VapC3)2	Min et al., 2012
	VapB5c	VapC5	M. tuberculosis	(VapB553−86)(VapC5)	Miallau et al., 2009
	VapB30	VapC30	M. tuberculosis	(VapB30)2(VapC30)2	Lee et al., 2015
	ω (regulator for ε-ζ, not antitoxin)		Streptococcus pyogenes pSM19035 tripartite TA system ω-ε-ζ	ε2ζ2 for the TA complex; ω2 for the regulator protein	Murayama et al., 2001; Meinhart et al., 2003
SpoVT/AbrB	MazE	MazF	E. coli	MazF2-MazE2-MazF2	Kamada et al., 2003; Loris et al., 2003; Zorzini et al., 2015
	VapB2	VapC2	Rickettsia felis	(VapC2)4(VapB2)2 (VapC2)4(VapC2)4	Maté et al., 2012
	VapB	VapC	Shigella flexneri	VapB4VapC4	Dienemann et al., 2011
Phd/YefMe	Phd	Doc	E. coli phage P1	Doc-Phd2-Doc	Arbing et al., 2010; Garcia-Pino et al., 2010
	YefM	YoeB	E. coli	YefM2YoeB	Kamada and Hanaoka, 2005
	YefM	YoeB	M. tuberculosis	unknownd	Kumar et al., 2008
Unknownf	aRelB	aRelE	Pyrococcus horikoshii OT3	(aRelB)2(aRelE)2	Takagi et al., 2005
Unknowng	VapB15	VapC15	M. tuberculosis	(VapB15)2(VapC15)2 (VapB15)(VapC15)2	Das et al., 2014

^aStructure was only available for the HigA antitoxin (Arbing et al., 2010).

^bStructure only solved for ParD in solution by NMR (Oberer et al., 2007).

^cN-terminal region of VapB5 could not be modeled but predicted to be RHH motif (Miallau et al., 2009).

^dTA complex possibly YefM₂YoeB; only YefM was crystalized (Kumar et al., 2008).

^eYefM was found to share structural similarity with the Phd antitoxin with strong conservation of the N-terminal DNA-binding domain, which are thus classified as having a Phd/YefM-like fold (Arbing et al., 2010).

^fDNA-binding domain unclear, potentially leucine zipper dimerization with N-terminal basic residues used for DNA recognition (Takagi et al., 2005).

^gN-terminal residues of VapB15 could not be modeled into the electron density (Das et al., 2014).