Small-angle X-ray scattering- and nuclear magnetic resonance-derived conformational ensemble of the highly flexible antitoxin PaaA2.

TitleSmall-angle X-ray scattering- and nuclear magnetic resonance-derived conformational ensemble of the highly flexible antitoxin PaaA2.
Publication TypeJournal Article
Year of Publication2014
AuthorsSterckx, Y. G. J., Volkov A.. N., Vranken W. F., Kragelj J., Jensen M. Ringkjøbi, Buts L., Garcia-Pino A., Jové T., Van Melderen L., Blackledge M., van Nuland N. A. J., and Loris R.
JournalStructure
Volume22
Issue6
Pagination854-65
Date Published2014 Jun 10
ISSN1878-4186
KeywordsAmino Acid Sequence, Antitoxins, Bacterial Toxins, Escherichia coli O157, Escherichia coli Proteins, Humans, Magnetic Resonance Spectroscopy, Models, Molecular, Molecular Sequence Data, Protein Conformation, Scattering, Small Angle, X-Ray Diffraction
Abstract

Antitoxins from prokaryotic type II toxin-antitoxin modules are characterized by a high degree of intrinsic disorder. The description of such highly flexible proteins is challenging because they cannot be represented by a single structure. Here, we present a combination of SAXS and NMR data to describe the conformational ensemble of the PaaA2 antitoxin from the human pathogen E. coli O157. The method encompasses the use of SAXS data to filter ensembles out of a pool of conformers generated by a custom NMR structure calculation protocol and the subsequent refinement by a block jackknife procedure. The final ensemble obtained through the method is validated by an established residual dipolar coupling analysis. We show that the conformational ensemble of PaaA2 is highly compact and that the protein exists in solution as two preformed helices, connected by a flexible linker, that probably act as molecular recognition elements for toxin inhibition.

DOI10.1016/j.str.2014.03.012
Alternate JournalStructure
PubMed ID24768114
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