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Unfolding transitions of Bacillus anthracis protective antigen

Lookup NU author(s): Dr David Allen Chalton, Ian Kelly, Professor Jeremy LakeyORCiD


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Protective antigen (PA) is an 83 kDa protein which, although essential for toxicity of Bacillus anthracis, is harmless and an effective vaccine component. In vivo it undergoes receptor binding, proteolysis, heptamerisation and membrane insertion. Here we probe the response of PA to denaturants, temperature and pH. We present analyses (including barycentric mean) of the unfolding and refolding behavior of PA and reveal the origin of two critical steps in the denaturant unfolding pathway in which the first step is a calcium and pH dependent rearrangement of domain 1. Thermal unfolding fits a single transition near 50 °C. We show for the first time circular dichroism (CD) spectra of the heptameric, furin-cleaved PA63 and the low-pH forms of both PA83 and PA63. Although only PA63 should reach the acidic endosome, both PA83 and PA63 undergo similar acidic transitions and an unusual change from a β II to a β I CD spectrum. © 2007 Elsevier Inc. All rights reserved.

Publication metadata

Author(s): Chalton DA, Kelly IF, McGregor A, Ridley H, Watkinson A, Miller J, Lakey JH

Publication type: Article

Publication status: Published

Journal: Archives of Biochemistry and Biophysics

Year: 2007

Volume: 465

Issue: 1

Pages: 1-10

ISSN (print): 0003-9861

ISSN (electronic): 1096-0384

Publisher: Academic Press


DOI: 10.1016/

PubMed id: 17531947


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Funder referenceFunder name
55979Wellcome Trust
56232Wellcome Trust
40422Wellcome Trust