Retracted: The activity of the pore-forming toxin lysenin is regulated by crowding

Publisher's notice concerning Nacho L.B. Munguira, Alfonso Barbas and Ignacio Casuso 2019 NanotechnologyThis article has been retracted by IOP Publishing following an institutional investigation by INSERM and AMU. The investigation concluded that the publication broke institutional rules and regulations. As a member of COPE, IOP Publishing agrees to honour the findings of the investigation and retract the paper, in line with COPE guidelines. (30 June 2020)The β pore-forming toxins (β-PFTs) are cytotoxic proteins produced as soluble monomers, which cluster and oligomerize at the membrane of the target host cells. Their initial oligomeric state, the prepore, is not cytotoxic. The β-PFTs undergo a large structural transition to a second oligomeric state, the pore, which pierces the membrane of the host cell and is cytotoxic. Data from electrophysiology and vesicle permeabilization experiments have suggested the possibility of a correlation between the transition rate from prepore state to pore state and the levels of local crowding in the cluster of β-PFT oligomers. Nevertheless, to this date, visualization and understanding at the molecular level are missing. We have addressed this issue using a panel of Atomic Force Microscopy (AFM) techniques and simulations. We describe the mechanism by which the rates of formation of the transmembrane pores correlate with the local levels of crowding for the β-PFT lysenin and discuss possible biological and medical implications.