Bidirectional attack on the actin cytoskeleton. Bacterial protein toxins causing polymerization or depolymerization of actin

The actin cytoskeleton is one of the major targets of bacterial protein toxins. The family of binary actin-ADP-ribosylating toxins, including Clostridium difficile transferase CDT, Clostridium perfringens iota toxin and Clostridium botulinum C2 toxin, modifies arginine-177 of actin. Thereby actin polymerization is blocked. By contrast, actin polymerization is facilitated by the tripartite Photorhabdus luminescens toxin complex including TccC3, which modifies actin at threonine-148. The review discusses both toxin families in respect to recent findings.