Fig. 5.

The sodium binding site in MurJ_TA. a Na⁺ is bound in the C-lobe (TMs 7, 11, 12) coordinated by Asp235, Asn374, Asp378, Val390 (backbone carbonyl), and Thr394. Fo − Fc omit density for Na⁺ is shown as magenta mesh contoured to 4.5 σ (peak height ~19 σ, 1.8 Å resolution). 2Fo − Fc omit density is shown in gray mesh. Na⁺ is coordinated by trigonal bipyramidal geometry. b Na⁺ was also bound in the inward-occluded and inward-closed structures. c Na⁺-associated rearrangement could be propagated down TM 7. d Complementation assay of MurJ_TA sodium site mutants in MurJ_EC-depletion strain NR1154. Cells transformed with plasmids encoding MurJ_TA (wild-type or sodium site mutant) or without insert (pEXT21) were depleted of endogenous MurJ by serial dilution on agar plates containing the anti-inducer d-fucose. MurJ_TA expression was induced by addition of IPTG. Data shown are representative of three biological replicates. Source data are provided as a Source Data File. Mutants D235A and N374A were previously determined to neither express nor complement²⁵