Table 1. Strains, plasmids, gene and primers used in this study.

Strain, plasmid, gene or primer	Relevant features or sequence (5’– 3’)	Reference
Strains
E. coli
DH5α	endA1 glnV44 thi-1 recA1 relA1 gyrA96 deoR F- Φ80dlacZΔM15 Δ(lacZYA-argF)U169, hsdR17(rK- mK+), λ–	Invitrogen
BL21 (DE3)	F–ompT gal dcm lon hsdSB (rB- mB-) λ(DE3)	Novagen
BL21 (DE3) BirA	BL21 (DE3) with biotin ligase gene	Novagen
L. lactis NZ9000	MG1363 nisRK ΔpepN	[28–31]
Plasmids
pET28b(+)	Kanr, E. coli expression vector	Novagen
pNZ8148	pSH71 derivative, PnisA, Cmr, nisin-controlled expression	[28–31]
pSDLBA3b	pNZ8148 containing gene fusion of spUsp-LEIS, b-dom and cA	[17]
pET28-Stx1B	pET28b containing Stx1B gene	This work
pET28- H6-TolA-Avi	pET28b containing tolA gene with AviTag on C-terminus	[12]
pET28-H6-S1Bx-TolA-Avi	pET28b containing gene fusion of different variants of S1B clones with TolA and AviTag	This work
pET28-H6-ABDwt-TolA-Avi	pET28b containing gene fusion of ABDwt with TolA and AviTag
pSD-S1B22	pNZ8148 containing gene fusion of Usp45 signal peptide, S1B22 and cA	This work
pSD-S1B26	pNZ8148 containing gene fusion of Usp45 signal peptide, S1B26 and cA	This work
pSD-ABDwt	pNZ8148 containing gene fusion of Usp45 signal peptide, ABDwt and cA	This work
pSD-H6-ABDwt	pNZ8148 containing gene fusion of Usp45 signal peptide, H6 tag, ABDwt and cA	This work
Gene
Stx1B	CCATGGCAAAAAAAACATTATTAATAGCTGCATCGCTTTCATTTTTTTCAGCAAGTGCGCTGGCGACGCCTGATTGTGTAACTGGAAAGGTGGAGTATACAAAATATAATGATGACGATACCTTTACAGTTAAAGTGGGTGATAAAGAATTATTTACCAACAGATGGAATCTTCAGTCTCTTCTTCTCAGTGCGCAAATTACGGGGATGACTGTAACCATTAAAACTAATGCCTGTCATAATGGAGGGGGATTCAGCGAAGTTATTTTTCGTCTCGAG	This work
Primer
setB-rev	ACCGCGGATCCAGGTAA	[11, 12]
EWT5-ABDforN1	TTCCTCCATGGGTATGAGAGGATCGCATCACCATCACCATCACCTGGCGGAAGCTAAAGTCTTAGCTAAC	[13]
EWT5-ABDforN2	TTCCTCCATGGGCAGCAGCCATCACCATCACCATCACCTGGCGGAAGCTAAAGTCTTAGCTAAC	[13]
ABD-F	GGATCCCTGGCGGAAGCTAAAGTC	This work
S1B22-R	GAATTCAGGTAAACGAGCTAAAATAGCATCTATC	This work
S1B26-R	GAATTCAGGTAACGCAGCTAAAATCCAATC	This work
ABDwt-R	GAATTCAGGTAATGCAGCTAAAATTTCATCTATC	This work
ABDH6-F	AGGATCCCATCACCATCACCATCAC	This work