Xenorhabdus nematophila alpha-xenorhabdolysin (XaxA) and Yersinia enterocolitica YaxA, and similar proteins
This model includes Xenorhabdus nematophila alpha-xenorhabdolysin (XaxA) and Yersinia enterocolitica YaxA, both parts of two-component alpha-helical pore-forming toxins (alpha-PFTs). The xaxAB genes encoding the XaxAB toxin have also been also identified in various plant and human pathogens. XaxAB triggers necrosis and apoptosis in both insect hemocytes and mammalian cells. Structure studies show that component A binds to component B's back, forming a subunit; twelve to fifteen of these subunits then conjoin as the pore-forming toxin. Component A stabilizes each subunit on the membrane and activates component B, which then punctures the membrane by swinging out its lower end. Similarly, Yersinia enterocolitica YaxA, encoded by the yaxAB gene, forms a pore predominantly composed of decamers of YaxA-YaxB heterodimers. Although both subunits bear membrane-active moieties, only YaxA is capable of binding to membranes by itself and YaxB is subsequently recruited to membrane-associated YaxA and induced to present its lytic transmembrane helices; pore formation then progresses by further oligomerization of YaxA-YaxB dimers. YaxAB has been found to be strongly upregulated by the Yersinia master regulator RovA, a transcriptional activator of Yersinia outer membrane protein invasion which is involved in bacterial attachment and invasion across the intestinal epithelium.
Comment:this is a two-component alpha-helical pore-forming toxin YaxAB, which forms a pore composed of decamers of YaxA-YaxB heterodimers
Structure:6EL1: Yersinia enterocolitica YaxA interacts with neighboring molecules that include YaxB, involved in forming an eicosameric structure to form a pore; contacts at 4.0A
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