Extended Data Figure 4: Functional assays of S. sonnei ZntA.

a, Wild-type and ΔHMBD (inset) S. sonnei ZntA ATPase activity is stimulated by Zn²⁺, Cd²⁺ and Pb²⁺. ATPase activity (normalized; the activity in the presence of Zn²⁺ is set at 100% for the wild type and ΔHMBD, respectively) was determined using the Baginski assay (see Methods for details). This ion stimulation profile matches the one observed for ZntA from E. coli⁵³. The mean + s.d. of technical replicates is shown (n = 3). b, Effect of K⁺, Na⁺ and Mg²⁺ on S. sonnei ZntA activity. The ATPase activity of wild-type S. sonnei ZntA in detergent micelles or upon reconstitution in proteoliposomes, in buffers containing exclusively Na⁺ or K⁺, as determined by the Baginski assay, is shown. For Mg²⁺, the activity was in the proteoliposomes for internal buffers with or without MgCl₂. The mean + s.d. of technical replicates is shown (n = 3). c, Zn²⁺ and H⁺ transport across vesicle membranes. Zn²⁺ transport of wild-type and D436N S. sonnei ZntA proteoliposomes monitored using the zinc-selective chelator FluoZin-1 (left). H⁺ counter-ion transport in wild-type S. sonnei ZntA or Ca²⁺-ATPase LMCA proteoliposomes monitored using the pH indicator pyranine (right).