Crystallization and X-ray crystallographic analysis of the cholesterol-dependent cytolysin listeriolysin O from Listeria monocytogenes

The secreted pore-forming toxin listeriolysin O (LLO) from the intracellular pathogen Listeria monocytogenes is a member of the family of cholesterol-dependent cytolysins (CDC) with broad properties in pathogenesis. Its role as a virulence factor is enigmatic: it disrupts membranes and acts as an inductor of both pro- and anti-inflammatory responses in infected cells. In addition, LLO is also a potent target for immunogenicity during infection. Natively secreted LLO from a recombinant L. innocua strain was crystallized in its water-soluble monomeric form. The crystals obtained belonged to the orthorhombic space group P2₁2₁2₁, with unit-cell parameters a = 26.7, b = 85.1, c = 230.0 Å, and diffracted to beyond 2.2 Å resolution. The Matthews coefficient and the solvent content were estimated to be 2.4 Å³ Da^-1 and 49.2%, respectively. The structure with one molecule in the asymmetric unit was solved using Phaser employing the structure of the previously characterized CDC toxin perfringolysin O as a search model.