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Toxins 2015, 7(7), 2598-2614; doi:10.3390/toxins7072598

Different Roles of N-Terminal and C-Terminal Domains in Calmodulin for Activation of Bacillus anthracis Edema Factor

1
Institute of Pharmacology, Hannover Medical School, Carl-Neuberg-Str. 1, Hannover D-30625, Germany
2
Institute of Pharmacy, University of Regensburg, Universitätsstr. 31, Regensburg D-93053, Germany
3
Ben May Department of Cancer Research, University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA
4
Department of Chemistry, University of Georgia, 140 Cedar Street, Athens, GA 30602-2556, USA
5
Department of Pharmacology and Toxicology, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Shihui Liu
Received: 29 April 2015 / Revised: 29 June 2015 / Accepted: 6 July 2015 / Published: 13 July 2015
(This article belongs to the Collection Anthrax Toxins)
View Full-Text   |   Download PDF [669 KB, uploaded 13 July 2015]   |  

Abstract

Bacillus anthracis adenylyl cyclase toxin edema factor (EF) is one component of the anthrax toxin and is essential for establishing anthrax disease. EF activation by the eukaryotic Ca2+-sensor calmodulin (CaM) leads to massive cAMP production resulting in edema. cAMP also inhibits the nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase, thus reducing production of reactive oxygen species (ROS) used for host defense in activated neutrophils and thereby facilitating bacterial growth. Methionine (Met) residues in CaM, important for interactions between CaM and its binding partners, can be oxidized by ROS. We investigated the impact of site-specific oxidation of Met in CaM on EF activation using thirteen CaM-mutants (CaM-mut) with Met to leucine (Leu) substitutions. EF activation shows high resistance to oxidative modifications in CaM. An intact structure in the C-terminal region of oxidized CaM is sufficient for major EF activation despite altered secondary structure in the N-terminal region associated with Met oxidation. The secondary structures of CaM-mut were determined and described in previous studies from our group. Thus, excess cAMP production and the associated impairment of host defence may be afforded even under oxidative conditions in activated neutrophils. View Full-Text
Keywords: Bacillus anthracis edema factor; adenylyl cyclase toxin; (oxidized) calmodulin; (oxidized) calmodulin mutants Bacillus anthracis edema factor; adenylyl cyclase toxin; (oxidized) calmodulin; (oxidized) calmodulin mutants
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Lübker, C.; Dove, S.; Tang, W.-J.; Urbauer, R.J.B.; Moskovitz, J.; Urbauer, J.L.; Seifert, R. Different Roles of N-Terminal and C-Terminal Domains in Calmodulin for Activation of Bacillus anthracis Edema Factor. Toxins 2015, 7, 2598-2614.

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