Structural basis for receptor recognition and pore formation of a zebrafish aerolysin‐like protein

Abstract

Various aerolysin-like pore-forming proteins have been identified from bacteria to vertebrates. However, the mechanism of receptor recognition and/or pore formation of the eukaryotic members remains unknown. Here, we present the first crystal and electron microscopy structures of a vertebrate aerolysin-like protein from Danio rerio, termed Dln1, before and after pore formation. Each subunit of Dln1 dimer comprises a b-prism lectin module followed by an aerolysin module. Specific binding of the lectin module toward high-mannose glycans triggers drastic conformational changes of the aerolysin module in a pH-dependent manner, ultimately resulting in the formation of a membrane-bound octameric pore. Structural analyses combined with computational simulations and biochemical assays suggest a pore-forming process with an activation mechanism distinct from the previously characterized bacterial members. Moreover, Dln1 and its homologs are ubiquitously distributed in bony fishes and lamprey, suggesting a novel fish-specific defense molecule.

Amaranthin-Like Proteins with Aerolysin Domains in Plants

“…Obviously, other types of oligomerization between AAT monomers may also be hypothesized based on protein association similar to the aerolysin from Aeromonas sp. ( Degiacomi et al, 2013 ), the aerolysin-containing lectin from L. sulphureus ( Tateno and Goldstein, 2003 ; Mancheno et al, 2005 ), or Dln1 from D. rerio ( Jia et al, 2016 ).…”

“…The L. sulphureus lectin purified from mushrooms consists of a β-trefoil scaffold resembling the ricin B domain, which specifically recognizes lactose, N -acetyl- D -lactosamine and other galactose-related saccharides ( Mancheno et al, 2005 ). Another hemolytic lectin Dln1 contains a jacalin-related domain, which binds to high-mannose glycans ( Jia et al, 2016 ). These proteins are structurally similar to AAT4 and were also used for the molecular modeling of AAT4.…”

“…The cucumber lectin AAT4 was modeled using the X-ray coordinates of amaranthin from A. caudatus (PDB code 1JLY; Transue et al, 1997 ), the aerolysin-like protein Dln1 from zebrafish ( Danio rerio , PDB code 5DI0; Jia et al, 2016 ), the hemolytic lectin from the mushroom Laetiporus sulphureus (PDB code 1W3F; Mancheno et al, 2005 ), the parasporin-2 toxin from Bacillus thuringiensis (PDB code 2ZTB) ( Akiba et al, 2009 ), and the Cry23Aa1/Cry37Aa1 toxin complex of B. thuringiensis (4RHZ) as templates. Homology modeling of AAT4 was performed with the YASARA Structure program ( Krieger et al, 2002 ), running on a 2.53 GHz Intel duo core Macintosh computer.…”

Membrane Perforation by the Pore-Forming Toxin Pneumolysin

“…Molecular dynamics (MD) simulations offer a promising alternative to resolve pore formation at the molecular scale. Previous MD simulations of αand β-PFTs (20)(21)(22)(23)(24)(25) were limited to either protein monomers or small oligomers. Simple rate models for the assembly and insertion process have been proposed (26,27), but the role of lipids and the process of pore opening have not been studied in detail.…”

Glabralysins, Potential New β-Pore-Forming Toxin Family Members from the Schistosomiasis Vector Snail Biomphalaria glabrata

“…PFTs are most commonly described in bacteria and are known to play a role in bacterial virulence [46,63,64]. However, more and more aerolysin-like molecules are being characterized in plants and animals, venomous or not [65][66][67][68][69][70][71][72][73][74]. Interestingly, Moran and collaborators reported in metazoan organisms a high number of genes encoding aerolysin homologues acquired by horizontal gene transfer (HGT) events from bacterial sources [73,74].…”