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The Solvent-Expoded C-Terminus of the Cytolysin A Pore-Forming Toxin Directs Pore Formation and Channel Function in Membranes

Sathyanarayana, Pradeep and Desikan, Rajat and Ayappa, Ganapathy K and Visweswariah, Sandhya S (2016) The Solvent-Expoded C-Terminus of the Cytolysin A Pore-Forming Toxin Directs Pore Formation and Channel Function in Membranes. In: BIOCHEMISTRY, 55 (42). pp. 5952-5961.

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Official URL: http://dx.doi.org/10.1021/acs.biochem.6b00593


Pore-forming toxins (PFTs) bind to cell membranes and form nanoscale pores that allow leakage of cellular components, resulting in cell death. The water-soluble, monomeric form of these toxins shows a dramatic conformational change during pore formation, as exemplified by crystal structures of the monomer and functional pore of cytolysin A (ClyA). The solvent-exposed, C-terminal residues of the protein are essential for activity, but the mechanism by which this region regulates pore formation remains unknown. We show here that deletion of the C-terminus of ClyA did not alter its ability to bind to the membrane or oligomerize in detergent. However, the truncated toxin lysed erythrocytes poorly, was more susceptible to proteolysis and thermal unfolding, and showed low calcein leakage from small unilamellar vesicles. Using fully atomistic molecular dynamics (MD) simulations, we find that deletion of C-terminal residues from the ClyA monomer significantly altered stability and unfolding trajectories in the transmembrane N-terminal helix, a region that is pivotal in maintaining the structural integrity of the helical bundle. MD simulations of pores with or without the C-terminus showed minor differences, implying that if oligomerization could be induced prior to the addition to vesicles, then an active pore could be generated. Via generation of oligomers in a detergent prior to the addition to vesicles, the truncated toxin could induce calcein leakage from vesicles, albeit to a lower extent. Therefore, regions of pore-forming toxins, not directly involved in the pore structure, are not passive players but have important roles in undergoing the transition through intermediary steps leading to successful pore formation in a membrane environment.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Department/Centre: Division of Interdisciplinary Sciences > Centre for Biosystems Science and Engineering
Date Deposited: 07 Dec 2016 05:01
Last Modified: 17 Oct 2018 07:03
URI: http://eprints.iisc.ac.in/id/eprint/55469

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