A molecular pin to study the dynamics of β-barrel formation in pore-forming toxins on erythrocytes: a sliding model

Abstract

gamma-Hemolysins are pore-forming toxins which develop from water-soluble monomers by combining two different 'albeit homologous' proteins. They form oligomeric pores in both cell and model membranes by undergoing a still poorly understood conformational rearrangement in the stem region. The stem is formed by three beta-strands, folded onto the core of the soluble protein and completely extended in the pore. We propose a new model to explain such a process. Seven double-cysteine mutants were developed by inserting one cysteine on the stretch that links the beta-hairpin to the core of the protein and another on different positions along the beta-strands. The membrane bound protein was blocked in a non-lytic state by S-S bond formation. Six mutants were oxidized as inactive intermediates, but became active after adding DTT. These results demonstrate that the stem extension can be temporarily frozen and that the beta-barrel formation occurs by beta-strand concerted step-by-step sliding.

Membrane Damage by an α-Helical Pore-forming Protein, Equinatoxin II, Proceeds through a Succession of Ordered Steps

“…Membrane-bound trapped intermediates are useful in studying mechanisms of pore formation at the membrane surface (40,41), especially when accessibility of the disulfide bonds is maintained in the bound form. For example, introduction of the disulfide bond between two domains of perfringolysin O blocks pore formation at the prepore state (40).…”

Residues Essential for Panton-Valentine Leukocidin S Component Binding to Its Cell Receptor Suggest Both Plasticity and Adaptability in Its Interaction Surface

“…LukE/LukD has been reported as a dermonecrotic toxin and involved in bullous impetigo [26]. The toxic action of leukotoxins results from a complex mechanism which has been described in the case of HlgA/HlgB [7], [27], [28], [29] and is characterized by: (i) binding of the S class component on the target cell membrane, which requires the presence of a specific receptor, (ii) recruitment of the F class component, (iii) dimerization possibly accompanied by conformational rearrangement, (iv) formation of an octameric prepore, and (v) pore formation across the membrane. During this process, both class S and F proteins are faced with a dual environment: a hydrophilic milieu, when secreted by the bacteria upon infection, and a hydrophobic milieu, when forming the pore in the membrane.…”

Large scale conformational transitions in β‐structural motif of gramicidin A: kinetic analysis based on CD and FT‐IR data

“…The results may be useful for the further development of local unfolding theory. The mechanisms observed in this work can be applied to massive transitions within β ‐motifs such as membrane insertion of PA63 channel of anthrax toxin or a sliding model of β ‐barrel pore formation by γ‐hemolysins . In these models, the simultaneous breaking of a great number of H‐bonds is implied and the problem of high energetic barriers is faced.…”