Structural and biochemical analysis of the unique interactions of the Campylobacter jejuni CorA channel protein with divalent cations.

CorA is a Mg ²⁺ channel that plays a key role in the homeostasis of intracellular Mg ²⁺ in bacteria and archaea. CorA consists of a cytoplasmic domain and a transmembrane domain and generates a Mg ²⁺ pathway by forming a pentamer in the cell membrane. CorA gating is regulated via negative feedback by Mg ²⁺ , which is accommodated by the pentamerization interface of the CorA cytoplasmic domain (CorA _CD ). The Mg ²⁺ -binding sites of CorA _CD differ depending on the species, suggesting that the Mg ²⁺ -binding modes and Mg ²⁺ -mediated gating mechanisms of CorA vary across prokaryotes. To define the Mg ²⁺ -binding mechanism of CorA in the Campylobacter jejuni pathogen, we structurally and biochemically characterized C. jejuni CorA _CD (cjCorA _CD ). cjCorA _CD adopts a three-layered α/β/α structure as observed in other CorA orthologs. Interestingly, cjCorA _CD exhibited enhanced thermostability in the presence of Ca ²⁺ , Ni ²⁺ , Zn ²⁺ , or Mn ²⁺ in addition to Mg ²⁺ , indicating that cjCorA _CD interacts with diverse divalent cations. This cjCorA _CD stabilization is mediated by divalent cation accommodation by negatively charged residues located at the bottom of the cjCorA _CD structure away from the pentamerization interface. Consistently, cjCorA _CD exists as a monomer irrespective of the presence of divalent cations. We concluded that cjCorA _CD binds divalent cations in a unique pentamerization-independent manner.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2024 Elsevier Inc. All rights reserved.)