Fig. 5.

Possible mechanism of Zn²⁺ transport by ZntB. a Calculated electrostatic potential (±5 kT e⁻¹) of ZntB (cross-section of the pore is shown) (b) same for Zn²⁺-bound soluble domain of StZntB and (c) Zn²⁺-free soluble domain of VpZntB. d Phyre2-based model of putative Zn²⁺-bound EcZntB using StZntB as a template (pdb id 3NWI). e Phyre2-based model of full-length apo StZntB using EcZntB as a template. f Putative mechanism of Zn²⁺ transport via ZntB. ZntB cross-section is shown schematically; Zn²⁺ and H⁺ are shown as yellow and cyan spheres, respectively; arrows indicate possible movements of trans membrane helix 1, which are possibly caused by Zn²⁺ and/or H⁺ binding, eventually leading to the change in electrostatic potential (from positive (blue) to negative (red)) within the pore that stimulates ion advancement through it