Analysis of the feasibility for XK to act as a manganese transporter. (A) Metal ion interaction analysis predicted 15 sites to which a Mn²⁺ ion could bind in XK. Arrows point to two predicted sites exposed to external environments or the pore, and their corresponding residues were also displayed. (B) The simulated trajectory of the Mn²⁺ movement through the pore formed by the helices of XK. At the beginning of the simulation, the Mn²⁺ ions were clustered in the same place. At 10 ns, Mn²⁺ binding to the predicted site (230t-232V-233L) triggered the pore to change from a compact closed conformation to an open basket shape, which facilitated the inward movement of the Mn²⁺ ion. Once the channel was in the open state, the Mn²⁺ inward movement might not be driven by the electrostatic interaction with the binding sites but be driven by a concentration gradient. The ribbon structure was rotated at 30, 40, and 50 ns, respectively, to illustrate that the Mn²⁺ ion moved through the pore. Arrows in the ribbon structures point to the Mn²⁺ ion located inside the pore during the simulation.