Structures of the Insecticidal Toxin Complex Subunit XptA2 Highlight Roles for Flexible Domains

Authors

Cole L. Martin, University of Alabama at BirminghamFollow
David W. Chester, University of Alabama at BirminghamFollow
Christopher D. Radka, University of KentuckyFollow
Lurong Pan, University of Alabama at BirminghamFollow
Zhengrong Yang, University of Alabama at BirminghamFollow
Rachel C. Hart, Vanderbilt University Medical CenterFollow
Elad M. Binshtein, Vanderbilt University Medical CenterFollow
Zhao Wang, Baylor College of MedicineFollow
Lisa Nagy, Jefferson State Community CollegeFollow
Lawrence J. DeLucas, Predictive Oncology Inc.Follow
Stephen G. Aller, University of Alabama at BirminghamFollow

Abstract

The Toxin Complex (Tc) superfamily consists of toxin translocases that contribute to the targeting, delivery, and cytotoxicity of certain pathogenic Gram-negative bacteria. Membrane receptor targeting is driven by the A-subunit (TcA), which comprises IgG-like receptor binding domains (RBDs) at the surface. To better understand XptA2, an insect specific TcA secreted by the symbiont X. nematophilus from the intestine of entomopathogenic nematodes, we determined structures by X-ray crystallography and cryo-EM. Contrary to a previous report, XptA2 is pentameric. RBD-B exhibits an indentation from crystal packing that indicates loose association with the shell and a hotspot for possible receptor binding or a trigger for conformational dynamics. A two-fragment XptA2 lacking an intact linker achieved the folded pre-pore state like wild type (wt), revealing no requirement of the linker for protein folding. The linker is disordered in all structures, and we propose it plays a role in dynamics downstream of the initial pre-pore state.

Document Type

Article

Publication Date

8-2023

Notes/Citation Information

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Digital Object Identifier (DOI)

https://doi.org/10.3390/ijms241713221

Funding Information

This research was supported by a UAB competitive COVID-19 relief award and start-up funds to S.G.A.

Repository Citation

Martin, Cole L.; Chester, David W.; Radka, Christopher D.; Pan, Lurong; Yang, Zhengrong; Hart, Rachel C.; Binshtein, Elad M.; Wang, Zhao; Nagy, Lisa; DeLucas, Lawrence J.; and Aller, Stephen G., "Structures of the Insecticidal Toxin Complex Subunit XptA2 Highlight Roles for Flexible Domains" (2023). Markey Cancer Center Faculty Publications. 393.
https://uknowledge.uky.edu/markey_facpub/393