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Recombinant anthrax protective antigen: Observation of aggregation phenomena by TEM reveals specific effects of sterols

Lookup NU author(s): Professor Robin Harris, Dr Andrei Soliakov, Professor Jeremy LakeyORCiD



This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


Negatively stained transmission electron microscope images are presented that depict the aggregation of recombinant anthrax protective antigen (rPA83 monomer and the PA63 prepare oligomer) under varying in vitro biochemical conditions. Heat treatment (50 degrees C) of rPA83 produced clumped fibrils, but following heating the PA63 prepare formed disordered aggregates. Freeze-thaw treatment of the PA63 prepare generated linear flexuous aggregates of the heptameric oligomers. Aqueous suspensions of cholesterol microcrystals were shown to bind small rPA83 aggregates at the edges of the planar bilayers. With PA63 a more discrete binding of the prepores to the crystalline cholesterol bilayer edges occurs. Sodium deoxycholate (NaDOC) treatment of rPA83 produced quasi helical fibrillar aggregate, similar but not identical to that produced by heat treatment. Remarkably, NaDOC treatment of the PA63 prepores induced transformation into pores, with a characteristic extended 8-barrel. The PA63 pores aggregated as dimers, that aggregated further as angular chains and closed structures in higher NaDOC concentrations. The significance of the sterol interaction is discussed in relation to its likely importance for PA action in vivo. (C) 2016 Elsevier Ltd. All rights reserved.

Publication metadata

Author(s): Harris JR, Soliakov A, Watkinson A, Lakey JH

Publication type: Article

Publication status: Published

Journal: Micron

Year: 2017

Volume: 93

Pages: 1-8

Print publication date: 01/02/2017

Online publication date: 15/11/2016

Acceptance date: 12/10/2016

Date deposited: 31/05/2017

ISSN (print): 0968-4328

Publisher: Elsevier


DOI: 10.1016/j.micron.2016.10.007


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