Membrane insertion of α-xenorhabdolysin in near-atomic detail release_lkvayjf2vvhj3mfbiehxx7qqqi

by Evelyn Schubert, Ingrid R Vetter, Daniel Prumbaum, Pawel A Penczek, Stefan Raunser

Released as a post by Cold Spring Harbor Laboratory.

2018  

Abstract

Alpha-Xenorhabdolysins (Xax) are alpha-pore-forming toxins (alpha-PFT) from pathogenic bacteria that form 1-1.3 MDa large pore complexes to perforate the host cell membrane. PFTs are used by a variety of bacterial pathogens as an offensive or defensive mechanism to attack host cells. Due to the lack of structural information, the molecular mechanism of action of Xax toxins is poorly understood. Here, we report the cryo-EM structure of the XaxAB pore complex from Xenorhabdus nematophila at an average resolution of 0.4 nm and the crystal structures of the soluble monomers of XaxA and XaxB at 0.25 nm and 0.34 nm, respectively. The structures reveal that XaxA and XaxB are built similarly and appear as heterodimers in the 12-15 subunits con-taining pore. The structure of the XaxAB pore represents therefore the first structure of a bi-component alpha-PFT. Major conformational changes in XaxB, including the swinging out of an amphipathic helix are responsible for membrane insertion. XaxA acts as an activator and stabilizer for XaxB that forms the actual transmembrane pore. Based on our results, we propose a novel structural model for the mechanism of action of Xax toxins.
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Date   2018-05-01
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