AI-driven mechanistic analysis of conformational dynamics in CNNM/CorC Mg2+ transporters

The CNNM/CorC Mg²⁺ transporters are widely conserved in eukaryotes (cyclin M [CNNM]) and prokaryotes (CorC) and participate in various biological processes. Previous structural analyses of the CorC transmembrane domain in the Mg²⁺-bound inward-facing conformation revealed the conserved Mg²⁺ recognition mechanism in the CNNM/CorC family; however, the conformational dynamics in the Mg²⁺ transport cycle remain unclear because structures in other conformations are unknown. Here, we used AlphaFold structure prediction to predict the occluded-like and outward-facing-like conformations of the CorC and CNNM proteins and identified conserved hydrophilic interactions close to the cytoplasmic side in these conformations. Molecular dynamics simulations and biochemical cross-linking showed that these conserved hydrophilic interactions are stable, especially in the outward-facing-like conformation. Furthermore, mutational analysis revealed that the residues involved in these hydrophilic interactions on the cytoplasmic side are important for Mg²⁺ transport in the CorC and CNNM proteins. Our work provides mechanistic insights into the transport cycle of the CNNM/CorC family.