Table 2.

Characteristics of the ACT constructs with the OVA epitope

ProteinInsertion point and flanking sequencesa% Activity vs wild type
BindingbInvasive ACb,cHemolyticb
ACT wild typeNone100 ± 11100 ± 12100 ± 15
ACT108/OVASSLAHG107 VL SIINFEKL VH 108HTAVDL97 ± 12101 ± 1195 ± 10
ACT133/OVAGLVTGM132 VY SIINFEKL GYT 134DGVVAS101 ± 1498 ± 997 ± 12
ACT233/OVASEATGG232 VL SIINFEKL VH 233LDRERI100 ± 996 ± 999 ± 14
ACT336/OVALKEYIG335 VL SIINFEKL VH 336QQRGEGNDd ND96 ± 9
ACT424/OVAGEVSDM423 VY SIINFEKL GYT 425AAVEAA96 ± 1097 ± 10102 ± 11
ACT594/OVAGDALLA593 CT SIINFEKL RT 594RGVTSG57 ± 6<214 ± 3
ACT607/OVAQVAGAS606 VY SIINFEKL GYT 608GAAAGA64 ± 766 ± 530 ± 4
ACT751/OVAARHEQL750 VY SIINFEKL GYT 752NSDGL103 ± 1193 ± 1040 ± 5
ACT926/OVAVLANAS925 CT SIINFEKL RT 926RIHYDG0 00
ACT1334/OVAGNDWFG1333 VL SIINFEKL VH 1334NTQARE98 ± 13102 ± 1497 ± 14
ACT1387/OVAVDKLGE1386 VY SIINFEKL GYT 1388GSSAYD85 ± 982 ± 975 ± 8
ACT1648/OVAVHDWYR1647 VL SIINFEKL-VH 1648DADHRV97 ± 1199 ± 1295 ± 12
  • a The OVA epitope sequence is underlined, and the flanking residues are indicated in boldface.

  • b Expressed as a percentage of wild-type ACT activity. The activities of the proteins were determined prior to ablation of the AC activity (insertion of a dipeptide insert between residues 188 and 189) as described in Materials and Methods. The activities represent average values ± standard deviations from at least three independent determinations performed in duplicate with three different toxin preparations (n = 6).

  • c Invasive activity was determined as the AC activity translocated into sheep erythrocytes and protected against digestion by extracellularly added trypsin (5).

  • d ND, not determined (no measurable AC activity).