Table 3. Residues important for NAD⁺ binding and reaction.

Region	Role	Iota toxin comparison (wt = 100)a	Chelt	Certhrax	Mav toxin	EFV toxin	TccC5	Vis toxin
	rearranges upon target binding, stabilizes last E of [QE]XE, may bind “vital N”, may reposition N-ribose ring	Y246	H62	Y279	Y686	Y345	Y734	F67
	binds N-ribose			T280	T687	T346	T735	S68
	reaction step 2, rearranges on target binding, aids rotation of O5D-PN bond, may “catch” oxacarbenium ion before transfer	Y251A: 0; Y251F: 90	T71	Y284	Y691	F350	(S738, S739}	Y72
Vital N	binds A-phosphate	N255		N288	N695	N354	N742	N76
	may position “vital N”	L258		L291	L698	L357	I745	L79
region B active site loop	binds A-phosphate		R43	R292	R699	R358	R746	R80
region 1	unclear	Y294	Y24	Y340	V729	Y393	Y773	Y116
region 1 R	binds A/N-phosphate	R295A: 0; R→K: 1	R25	R341	R730	R394	R774	R117
region 1 R	binds nicotinamide	R296; (backbone H bond)	A26	R342	G731	G395	V775	G118
	binds A-riboseb (2 residues)	E301A: 0	S28	∼343–348 (S344}	∼732–737 (T732, N733 }	∼396–400 (N399, E400}	∼776–780; (T777}	∼119–123 (W120 }
	binds adeninec (1–2 residues)	Y333?	Y41?	∼380–384 (Q382, N384}	∼748–752; (E750}	∼410–412	∼802–806	∼135–139 (E137}
Region 2 STS	unclear	F336	F77	Y385	F753	F413	Y807	F140
region 2 STS	positions last E of [QE]XE via H-bonds, stabilizes oxacarbenium ion	S338A: 5	S79	S387	S755	S415	S809	S142
region 2 STS	stiffens active site via H bonds to nearby β-sheet	T339A: 20	T80	T388	T756	T416	T810	T143
region 2 STS	orients ARTT loop and [QE] of [QE]-X-E	S340A: 25	T81	S389	S757	S417	S811	S144
PN loop (region E)	stacking interaction with nicotinamide; mobile	F349A: 0; F349Y: 20		Y398	F768	F426	F819	F153
PN loop (region E)	binds N-phosphate	R352A: 0		R402	∼769–773	R437	R829	R166
ARTT loop	Target recognition, may reorient on ligand binding; can bind last E of [QE]XE	Y375	H125	Y426	Y790			Y186
ARTT loop	reaction step 3, substrate specificity; (mobile)	E378A: 0; E378D: 0; E378Q: 0	E128	Q429	E793	E461	Q884	E189
region 3 EXE	binds N-ribose, reaction step 1	E380A: 0; E380D: 0	E130	E431	E795	E463	E886	E191
Region 3	Unclear	L382	L59	L433	L797	L465	L888	L193

^aThese data apply to the homolog iota toxin and is rounded and reproduced from [33], [122].

^bPossible range given, followed by residues most likely involved; protein backbone H-bonding.

^cPossible range given, followed by residues most likely involved.