The actin and Rho-modifying toxins PTC3 and PTC5 ofPhotorhabdus luminescens: enzyme characterization and induction of MAL/SRF-dependent transcription

Rho-modifying bacterial protein toxins from Photorhabdus species

“…Sequence comparisons with other toxin ADP-ribosyltransferases and mutational analyses of TccC5 indicate that the Photorhabdus toxin belongs to the clostridial toxin-like ADP-ribosyltransferase (ARTC) subfamily of ADP-ribosyltransferases (Hottiger et al, 2010;Lang et al, 2010;Pfaumann et al, 2015). Typical for this subfamily is an RSE motif with arginine and serine residues involved in NAD-binding and a so-called "catalytic" glutamate (Domenighini et al, 1994).…”

“…Typical for this subfamily is an RSE motif with arginine and serine residues involved in NAD-binding and a so-called "catalytic" glutamate (Domenighini et al, 1994). In the case of TccC5, the RSE residues are Arg774, Ser809 and Glu886 (Pfaumann et al, 2015). Major protein substrates of TccC5-induced ADP-ribosylation are RhoA, B and C, Rac1-3 and Cdc42.…”

“…Major protein substrates of TccC5-induced ADP-ribosylation are RhoA, B and C, Rac1-3 and Cdc42. A minor substrate is the Rho subfamily protein Tc10 (Pfaumann et al, 2015). Interestingly, also plant Rac-like proteins are at least in vitro substrates with a strong modification of Rop4.…”

“…This turns the molecular switches into a constitutively activated state (Lang et al, 2010;Aktories, 2011) and explains why TccC5 causes strong stress-fiber formation. Toxin-induced persistently activated RhoA activates Rho kinase and formins, which cause actin polymerization and stress fiber formation (Matsui et al, 1996;Leung et al, 1996;Ishizaki et al, 1997;Lang et al, 2010;Pfaumann et al, 2015). In vitro assays showed that also Rac and Cdc42 are activated, which should result in lamellipodia and filopodia formation Nobes and Hall, 1995).…”

“…Model of the holotoxin by fitting the TcdA1 and TcdB2-TccC3 crystal structure into the cryo-EM structure of the holotoxin complex obtained from (Meusch et al, 2014). the activity state of RhoA after CNF1-treatment is increased for 2e4 h but returns to basal levels after 18 h, although the protein was still deamidated (Pfaumann et al, 2015). Similarly, the activity of Rac protein increases after CNF1 and TccC5 treatment for 2e6 h, whereas Rac activity decreases after 18 h in the case of CNF1, while it is stable with TccC5.…”