Figure 4.

Amino acid sequence of Shiga toxin 2a (Stx2a) A subunit and the identified cleavage sites induced by specific enzymes or components present in human stool. The amino acid sequence of the A subunit of Stx2a with highlighted signal peptide (purple) is displayed. Cleavage of Shiga toxin 2a (Stx2a) A subunit results in the generation of two fragments, A1 and A2, which are held together by a disulfide bond (SS-bond) located between the two cysteine residues (highlighted in grey). The conserved amino acid motif, where cleavage of Stx2a A subunit was postulated to occur, is highlighted in yellow, whereas the located cleavage sites induced by furin (green), trypsin (blue) or components present in stool from healthy human donors (blue and red) are indicated with arrows, respectively. * Furthermore, the cleavage site potentially induced by chymotrypsin-like elastase 3B (CELA3B) is also depicted (red).