Cryo-EM structure of the MgtE Mg 2+ channel pore domain in Mg 2+ -free conditions reveals cytoplasmic pore opening

Here, we determined the cryoelectron microscopy (cryo-EM) structure of the MgtE-Fab complex in the absence of Mg ions. The Mg-free MgtE transmembrane domain structure and its comparison with the Mg-bound, closed-state structure, together with functional analyses, showed the Mg-dependent pore opening of MgtE on the cytoplasmic side and revealed the kink motions of the TM2 and TM5 helices at the glycine residues, which are important for channel activity. Overall, our work provides structure-based mechanistic insights into the channel gating of MgtE.