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The Two-State Prehensile Tail of the Antibacterial Toxin Colicin N

Lookup NU author(s): Dr Christopher Johnson, Dr Alexandra Solovyova, Dr Helen Waller, Professor Jeremy Lakey

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

© 2017 Biophysical Society Intrinsically disordered regions within proteins are critical elements in many biomolecular interactions and signaling pathways. Antibacterial toxins of the colicin family, which could provide new antibiotic functions against resistant bacteria, contain disordered N-terminal translocation domains (T-domains) that are essential for receptor binding and the penetration of the Escherichia coli outer membrane. Here we investigate the conformational behavior of the T-domain of colicin N (ColN-T) to understand why such domains are widespread in toxins that target Gram-negative bacteria. Like some other intrinsically disordered proteins in the solution state of the protein, ColN-T shows dual recognition, initially interacting with other domains of the same colicin N molecule and later, during cell killing, binding to two different receptors, OmpF and TolA, in the target bacterium. ColN-T is invisible in the high-resolution x-ray model and yet accounts for 90 of the toxin's 387 amino acid residues. To reveal its solution structure that underlies such a dynamic and complex system, we carried out mutagenic, biochemical, hydrodynamic and structural studies using analytical ultracentrifugation, NMR, and small-angle x-ray scattering on full-length ColN and its fragments. The structure was accurately modeled from small-angle x-ray scattering data by treating ColN as a flexible system, namely by the ensemble optimization method, which enables a distribution of conformations to be included in the final model. The results reveal, to our knowledge, for the first time the dynamic structure of a colicin T-domain. ColN-T is in dynamic equilibrium between a compact form, showing specific self-recognition and resistance to proteolysis, and an extended form, which most likely allows for effective receptor binding.


Publication metadata

Author(s): Johnson CL, Solovyova AS, Hecht O, Macdonald C, Waller H, Grossmann JG, Moore GR, Lakey JH

Publication type: Article

Publication status: Published

Journal: Biophysical Journal

Year: 2017

Volume: 113

Issue: 8

Pages: 1673-1684

Print publication date: 17/10/2017

Online publication date: 17/10/2017

Acceptance date: 02/08/2017

ISSN (print): 0006-3495

ISSN (electronic): 1542-0086

Publisher: Biophysical Society

URL: https://doi.org/10.1016/j.bpj.2017.08.030

DOI: 10.1016/j.bpj.2017.08.030


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