Insight into the Structural Dynamics of the Lysenin During Prepore-to-Pore Transition Using Hydrogen–Deuterium Exchange Mass Spectrometry

Lysenin is a pore-forming toxin of the aerolysin family, which is derived from coelomic fluid of the earthworm Eisenia fetida. Upon binding to sphingomyelin (SM)-containing membranes, lysenin undergoes a series of structural changes promoting the conversion of water-soluble monomers into oligomers, leading to its insertion into the membrane and the formation of a lytic β-barrel pore. The soluble monomer and transmembrane pore structures were recently described, but the underlying structural details of oligomerization remain unclear. To investigate the molecular mechanisms controlling the conformational rearrangements accompanying pore formation, we compared the hydrogen–deuterium exchange pattern between lysenin(WT) and its mutant lysenin(V88C/Y131C). This mutation arrests lysenin oligomers in the prepore state at the membrane surface and does not affect the structural dynamics of the water-soluble form of lysenin. In contrast, membrane-bound lysenin(V88C/Y131C) exhibited increased structural stabilization, especially within the twisted β-sheet of the N-terminal domain. We demonstrated that the structural stabilization of the lysenin prepore started at the site of lysenin’s initial interaction with the lipid membrane and was transmitted to the twisted β-sheet of the N-terminal domain, and that lysenin(V88C/Y131C) was arrested in this conformation. In lysenin(WT), stabilization of these regions drove the conformational changes necessary for pore formation.