FIG. 1.

Construction of the genetic CTB fusion proteins. (A) Addition of the 17-amino-acid OVA peptide to the C terminus of CTB. (B) Insertion of the 13-amino-acid HA peptide into the CTB molecule, replacing residues 56 to 64 of the mature protein and resulting in a protein of 107 instead of 103 amino acids. The first residue of the peptide and residue 55 of CTB are both serine. Additionally, the last residue of the peptide and residue 63 of CTB are both lysine. Open rectangles, HA or OVA peptide; solid rectangles, mature CTB protein. The serine residue at position 55 and the lysine residue at position 63 of CTB that are shared with the peptide sequence in CTB55-64HA are boxed.