ABC toxins are a recently discovered class of bacterial pore-forming proteins found in a wide range of insecticidal bacteria and some mammalian pathogens. Recent studies of prototypical toxins from this family have elucidated aspects of their structure and function, which shares some commonalities with the mode of action of binary toxins. Despite recent advances, details defining their mechanism of target recognition, toxin translocation and delivery are only partially understood, primarily because only a single example - the PTC3 toxin isolated from the insecticidal bacterium, Photorhabdus luminescens - has been extensively characterised. Here we report the first complete structures of both the soluble pre-pore, and a lipid nanodisc-embedded pore-forming conformation of a native ABC holotoxin assembly derived from the insecticidal bacterium Yersinia entomophaga (YenTc). YenTc has a divergent molecular architecture, incorporating enzymatically active chitinase subunits which are thought to underpin the potent oral and symbiont-independent activity exhibited by YenTc. We describe for the first time the structural mechanism via which these chitinases are incorporated into the membrane binding component, a mechanism which unexpectedly shares similarities with bacterial adhesins that are the building blocks of pili and fimbriae. Phylogenetic analyses indicate that chitinase incorporation is a feature of a small, recently evolved subset of ABC toxins, suggesting that this feature confers functional advantages over the more widely studied ancestral forms of the toxin. We also show that recombination of the two toxin components into a functional holotoxin is facilitated by a structural mechanism that is completely conserved with other ABC toxins, explaining how chimeric toxins derived from different pathogenicity islands and even diverse species can recombine into functional assemblies.