Figure 2.
VacA allelic diversity and structure—(A) significant allelic diversity exists in three regions of the VacA gene: the signal region (s1 and s2), the intermediate region (i1, i2, and i3) and the mid-region (m1 and m2); (B) the Signal Sequence allows for the passage of the pro-toxin across the inner-bacterial membrane. The passenger toxin domain consists of the N-terminal VacA fragment (p33) and the C-terminal VacA fragment (p55). The auto-transporter domain allows the toxin to translocate across the outer-bacterial membrane by forming a β-barrel. The p33 and p55 fragments may be cleaved from the β-barrel domain at some point during transit to, or in, the extracellular milieu to form the mature virulent subunits. Arrows indicate cleavage sites.