Aerolysin is the founding member of a superfamily of β-pore–forming toxins whose pore structure is unknown. We have combined X-ray crystallography, cryo-EM, molecular dynamics and computational modeling to determine the structures of aerolysin mutants in their monomeric and heptameric forms, trapped at various stages of the pore formation process. A dynamic modeling approach based on swarm intelligence was applied, whereby the intrinsic flexibility of aerolysin extracted from new X-ray structures was used to fully exploit the cryo-EM spatial restraints. Using this integrated strategy, we obtained a radically new arrangement of the prepore conformation and a near-atomistic structure of the aerolysin pore, which is fully consistent with all of the biochemical data available so far. Upon transition from the prepore to pore, the aerolysin heptamer shows a unique concerted swirling movement, accompanied by a vertical collapse of the complex, ultimately leading to the insertion of a transmembrane β-barrel.
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- Video 1: Aerolysin pore formation via a swirling mechanism (35.95 MB, Download)
- The movie shows a top and a side view of a morphing from the prepore (Fig. 2) to the pore models (Fig. 5). Conversion from one protein arrangement to the other is possible via a swirling mechanism, which can take place without any relevant topological bottlenecks (Fig. 6). Aerolysin domain 1 is not shown in the movie for sake of clarity.
- Supplementary Text and Figures (1,766 KB)
Supplementary Results, Supplementary Table 1 and Supplementary Figures 1–9.