Ca2+ Efflux Facilitated by Co-transport of Inorganic Phosphate Anion in the H+/ca2+ Antiporter YfkE

Authors

Wei Niu
Wenchang Zhou
Shuo Lu
Trung Vu
Vasanthi Jayaraman
José D Faraldo-Gómez
Lei Zheng

Publication Date

5-29-2023

Journal

Communications Biology

Abstract

Ca2+ is an important signaling messenger. In microorganisms, fungi, and plants, H+/Ca2+ antiporters (CAX) are known to play key roles in the homeostasis of intracellular Ca2+ by catalyzing its efflux across the cell membrane. Here, we reveal that the bacterial CAX homolog YfkE transports Ca2+ in two distinct modes: a low-flux H+/Ca2+ exchange mode and a high-flux mode in which Ca2+ and phosphate ions are co-transported (1:1) in exchange for H+. Coupling with phosphate greatly accelerates the Ca2+ efflux activity of YfkE. Our studies reveal that Ca2+ and phosphate bind to adjacent sites in a central translocation pathway and lead to mechanistic insights that explain how this CAX alters its conserved alpha-repeat motifs to adopt phosphate as a specific “transport chaperon” for Ca2+ translocation. This finding uncovers a co-transport mechanism within the CAX family that indicates this class of proteins contributes to the cellular homeostasis of both Ca2+ and phosphate.

Keywords

Calcium, Molecular modelling, Transporters, Permeation and transport, Ion transport