Fig. 3: Conformational changes induced by ATP binding.

a–c Side view of mClC-3 in apo and ATP bound states with Cl^- ions shown in green. d Sliced view of mClC-3_ATP shows four Cl^- ions binding sites in the transmembrane domains (TMD). The surface is colored by electrostatic potential (red, 10 kTe⁻¹; blue, +10 kTe⁻¹). e, f The four sites for Cl^- ion binding in mClC-3 in apo and ATP bound states. Cl^- ions are shown in green with their electron density mesh displayed. Residues close to these sites are shown. g The schematic diagram of the positions of the portals for the chloride ion and proton near CBS domains. h The portal outlined with green dashed line for the Cl^- ion in the bottom view in mClC-3_ATP, mClC-3_AMP and mClC-3_apo. The surface is colored by electrostatic potential. K521 residue was outlined in pink. i One subunit in mClC-3_ATP, mClC-3_AMP and mClC-3_apo was compared in the bottom view, revealing specific conformational changes of the residues near the S_in Cl^- ion. j The current ratio after about five minutes of 10 mM ATP stimulation to the initial current of ClC-3 mutant K521A and K521D (based on the mClC-3b_S3/S2/S1 background). Mean ± S.E.M. from biologically independent cells, n = 5. Two-sided t-test, the exact P values were labeled. k The two sites of H₂O of mClC-3 in apo, AMP bound and ATP bound states observed near the proton entrance. H₂O molecules are shown in red with their electron density mesh displayed. Residues close to these sites are shown. l The specific conformational changes observed by structural alignment of mClC-3_ATP, mClC-3_AMP and mClC-3_apo. Residues lining the H⁺ ion transport pathway showed altered sidechain orientations. m The water molecules in mClC-3_AMP interacting with E339 and E631 simultaneously, suggesting the possibility of proton transport between the two residues.