Download MendeleyMolecular mechanisms of mitochondrial Ca 2+ exchanger NCLX.
Zhang, L., Han, Y., Zeng, W., Xue, J., Wang, Y., Jiang, Y.(2026) Nat Commun
- PubMed: 42431881 Search on PubMed
- DOI: https://doi.org/10.1038/s41467-026-75483-x
- Primary Citation Related Structures:
9Z4I, 9Z4J - PubMed Abstract:
Mitochondrial Ca²⁺ homeostasis is maintained through coordinated influx and efflux processes, with NCLX long recognized as the primary Ca²⁺ extruder operating via Na⁺/Ca²⁺ exchange. Here, we report cryo-EM structures of rat NCLX in cytosolic-facing occluded and open states. The central transmembrane (TM) domain of NCLX comprises ten helices arranged in two inverted, structurally similar halves, with two α-repeats forming a central ion-binding pocket. Peripheral TMs 1 and 6 are loosely associated with the core and likely mediate alternative access to this site. These structural features closely resemble those of NCXs, indicating a conserved ion exchange mechanism. While NCLX retains the canonical Ca²⁺-binding site, it lacks several key Na⁺-binding residues found in NCXs, suggesting broader ion selectivity. Consistently, cell-based Ca²⁺ uptake assays show that NCLX mediates Ca²⁺ exchange using Na⁺, K⁺, Li⁺, and potentially protons as counterions. Based on the structural symmetry of NCLX and its bidirectional exchange capability, we propose a matrix-facing model and an alternating-access mechanism in which TMs 1 and 6 undergo sliding motions to enable ion exchange between cytosolic and matrix sides, analogous to NCX. These findings provide a structural and mechanistic framework for understanding NCLX-mediated Ca²⁺ transport in mitochondria.
- Department of Physiology, The University of Texas Medical Center, Dallas, TX, USA.
Organizational Affiliation:
