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Hydrophobic Gating and 1/f Noise of the Anthrax Toxin Channel

Yamini, G and Kanchi, S and Kalu, N and Momben Abolfath, S and Leppla, SH and Ayappa, KG and Maiti, PK and Nestorovich, EM (2021) Hydrophobic Gating and 1/f Noise of the Anthrax Toxin Channel. In: The journal of physical chemistry. B, 125 (21). pp. 5466-5478.

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Official URL: https://doi.org/10.1021/acs.jpcb.0c10490


"Pink" or 1/f noise is a natural phenomenon omnipresent in physics, economics, astrophysics, biology, and even music and languages. In electrophysiology, the stochastic activity of a number of biological ion channels and artificial nanopores could be characterized by current noise with a 1/f power spectral density. In the anthrax toxin channel (PA63), it appears as fast voltage-independent current interruptions between conducting and nonconducting states. This behavior hampers potential development of PA63 as an ion-channel biosensor. On the bright side, the PA63 flickering represents a mesmerizing phenomenon to investigate. Notably, similar 1/f fluctuations are observed in the channel-forming components of clostridial binary C2 and iota toxins, which share functional and structural similarities with the anthrax toxin channel. Similar to PA63, they are evolved to translocate the enzymatic components of the toxins into the cytosol. Here, using high-resolution single-channel lipid bilayer experiments and all-atom molecular dynamic simulations, we suggest that the 1/f noise in PA63 occurs as a result of "hydrophobic gating" at the �-clamp region, the phenomenon earlier observed in several water-filled channels "fastened" inside by the hydrophobic belts. The �-clamp is a narrow "hydrophobic ring" in the PA63 lumen formed by seven or eight phenylalanine residues at position 427, conserved in the C2 and iota toxin channels, which catalyzes protein translocation. Notably, the 1/f noise remains undetected in the F427A PA63 mutant. This finding can elucidate the functional purpose of 1/f noise and its possible role in the transport of the enzymatic components of binary toxins.

Item Type: Journal Article
Publication: The journal of physical chemistry. B
Publisher: NLM (Medline)
Additional Information: The copyright for this article belongs to American Chemical Society
Department/Centre: Division of Mechanical Sciences > Chemical Engineering
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 27 Aug 2021 11:15
Last Modified: 27 Aug 2021 11:15
URI: http://eprints.iisc.ac.in/id/eprint/69320

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