The diverse landscape of AB5-type toxins.

AB-type toxins are a group of secreted protein toxins that are central virulence factors for bacterial pathogens such as and certain lineages of pathogenic and . AB toxins are composed of an active (A) subunit that manipulates host cell biology in complex with a pentameric binding/delivery (B) subunit that mediates the toxin's entry into host cells and its subsequent intracellular trafficking. Broadly speaking, all known AB-type toxins adopt similar structural architectures and employ similar mechanisms of binding, entering and trafficking within host cells.

The evolutionary diversification of the toxin locus.

is a diverse species of bacterial pathogens comprised of >2,500 serovars with variable host ranges and virulence properties. Accumulating evidence indicates that two AB-type toxins, typhoid toxin and ArtAB toxin, contribute to the more severe virulence properties of the strains that encode them. It was recently discovered that there are two distinct types of -like genetic elements in : those that encode ArtAB toxins ( elements) and those in which the gene is degraded and the ArtB homolog, dubbed PltC, serves as an alternative delivery subunit for typhoid toxin ( elements).

Mechanistic insight into bacterial entrapment by septin cage reconstitution.

Septins are cytoskeletal proteins that assemble into hetero-oligomeric complexes and sense micron-scale membrane curvature. During infection with Shigella flexneri, an invasive enteropathogen, septins restrict actin tail formation by entrapping bacteria in cage-like structures. Here, we reconstitute septin cages in vitro using purified recombinant septin complexes (SEPT2-SEPT6-SEPT7), and study how these recognize bacterial cells and assemble on their surface.