Table 1. Effect of C-terminal mutations on the in vitro actin nucleation activity and in vivo virulence functions of IpaC.
| Mutant | Actin nucleationa | Relative invasion (%)b | Contact hemolysis (%)c |
|---|---|---|---|
| IpaC | Yes | 100±9 | 100±1 |
| IpaCΔI | Yes | 0±0 | 8±3 |
| IpaCΔIII | No | 0±0 | 6±3 |
| IpaCΔ344-363 | No | 0±0 | 100±6 |
| IpaCStag | No | 0±0 | 100±5 |
| SipC | Yes | 0±0 | 10±5 |
This is an in vitro activity that involves purified protein and thus does not depend upon active type III secretion.
Invasion is relative to a positive control (SF621 complemented with ipaC), which gave 153±14 invading bacteria per well. (n=3)
Relative hemolysis is also related to SF621 complemented with ipaC. In this case, 100% is actually complete lysis of the RBCs. It is noteworthy that complete absence of ipaC still allows 5 to 10% hemolysis due to the residual activity of IpaB, which is inserted into the erythrocyte membranes even in the absence of IpaC.