FIG. 2.

Illustration of histidine-tagged StxB1 and StxB2 and the seven histidine-tagged chimeric StxB1/StxB2 proteins. StxB1 is shown in black, while Stx2 is shown in white; the six-histidine tags at the C termini are speckled. The names of the seven chimeric proteins are shown to the left of the respective chimeric proteins, and the regions of StxB1 are listed beneath the chimeric B subunits. The first region in the StxB1 subunit, region A, consists of residues 1 to 6, while the second region, B, spans residues 25 to 32 and the third region, C, ranges from amino acids 54 to 61. The two cysteine residues in each B subunit are denoted by bars above the B subunits.