Insecticidal toxin complex (TC) component, TcaA (1095 aas) (may mediate toxin-C internalization)(Landsberg et al., 2011).  The TcdA1 prepore assembles as a pentamer forming an α-helical, vuvuzela-shaped channel less than 1.5 nanometres in diameter surrounded by a large outer shell (Gatsogiannis et al. 2013). Membrane insertion is triggered not only at low pH as expected, but also at high pH, explaining Tc action directly through the midgut of insects. Comparisons with structures of the TcdA1 pore inserted into a membrane and in complex with TcdB2 and TccC3 reveal large conformational changes during membrane insertion, suggesting a novel syringe-like mechanism of protein translocation (Gatsogiannis et al. 2013).  P. luminescens is a nematode symbiont and an insect pathogen.  The toxin, TcC, of the tripartite toxin complex, is an ADP ribosyl transferase causing actin clustering, defects in phagocytosis and cell dealth.