Structural, physicochemical and dynamic features conserved within the aerolysin pore-forming toxin family

Nuria Cirauqui,Matteo Dal Peraro,F Gisou Van Der Goot,Luciano A Abriata

doi:10.1038/s41598-017-13714-4

Nuria Cirauqui, Matteo Dal Peraro + Show 2 more

Open Access

https://doi.org/10.1038/s41598-017-13714-4

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Abstract

Aerolysin is the founding member of a major class of β-pore-forming toxins (β-PFTs) found throughout all kingdoms of life. PFTs are cytotoxic proteins produced as soluble monomers, which oligomerize at the membrane of target host cells forming pores that may lead to osmotic lysis and cell death. Besides their role in microbial infection, they have become interesting for their potential as biotechnological sensors and delivery systems. Using an approach that integrates bioinformatics with molecular modeling and simulation, we looked for conserved features across this large toxin family. The cell surface-binding domains present high variability within the family to provide membrane receptor specificity. On the contrary, the novel concentric double β-barrel structure found in aerolysin is highly conserved in terms of sequence, structure and conformational dynamics, which likely contribute to preserve a common transition mechanism from the prepore to the mature pore within the family.Our results point to the key role of several amino acids in the conformational changes needed for oligomerization and further pore formation, such as Y221, W227, P248, Q263 and L277, which we propose are involved in the release of the stem loop and the two adjacent β-strands to form the transmembrane β-barrel.

Highlights

Pore-forming toxins (PFTs) are cytotoxic proteins produced by a variety of organisms
Five other 5 aerolysin-like toxin structures were solved in their soluble form, namely the epsilon-toxin (ETX) from the anaerobic Gram-positive Clostridium perfringens[7], parasporin-2 from Bacillus thuringiensis[8], Laetiporus sulphureus lectin (LSL) from the mushroom Laetiporus sulphureus[9], lysenin from the earthworm Eisenia fetida[10], and Dln[1] from Danio regio[11]
Cryo-EM structures at near-atomic resolution have been reported for aerolysin mutants arrested at different stages of pore formation, namely the prepore[20] (PDB entry 5JZH), post-prepore[20] (PDB entry 5JZW), and quasi-pore states[20] (PDB entry 5JZW), together with a low resolution pore conformation[20] (PDB entry 5JZT), making this toxin the best characterized among all β-pore-forming toxins (β-PFTs)

Summary

Introduction

Pore-forming toxins (PFTs) are cytotoxic proteins produced by a variety of organisms. Five other 5 aerolysin-like toxin structures were solved in their soluble form, namely the epsilon-toxin (ETX) from the anaerobic Gram-positive Clostridium perfringens[7], parasporin-2 from Bacillus thuringiensis[8], Laetiporus sulphureus lectin (LSL) from the mushroom Laetiporus sulphureus[9], lysenin from the earthworm Eisenia fetida[10], and Dln[1] from Danio regio[11] All these aerolysin-like proteins share a similar monomeric architecture, with a variable membrane-binding (MB) domain and a structurally conserved pore-forming (PF) region, presenting five β-strands with an insertion loop (stem loop (SL)) between strands β2 and β3 (Fig. 1a)[6]. Besides these conserved features shared across the family, lateral domains surrounding the central DBB structure are instead very variable, possibly to confer specificity for membrane receptors, producing a high degree of modularity for this PFT family

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