Fig. 3: ZorAB is a PG-binding, proton-driven motor.

a, EcZorAB viewed from the plane of the membrane, with ZorB shown as ribbons (black and white) and ZorA shown as a translucent surface. The distance between the inner membrane and PG layer in E. coli is approximately 90 Å (ref. ³²). The cysteine residues from the two disulfide bridges in the ZorB PGBD are indicated and shown as spheres. The Asp26 residues from both ZorB TM helices are indicated and shown. b, Top view of the ZorB PGBD. c, Cross-section view of the ZorAB TMD, showing ZorB Asp26 and the surrounding residues. d, Magnified view of the interactions between ZorB and ZorA at the domain assembly interface in the periplasmic space. e, The Ca²⁺-binding site. EM densities are only overlapped on Ca²⁺ ion, and the two water molecules. f, Magnified view of the interactions between the ZorB N terminus and the ZorA tail. g, Ion-translocation pathway (semitransparent surface representation in light blue) in ZorAB. Residues along the ion-permeation pathway and from the ion-selectivity filter are shown. Each asterisk indicates residues or structural elements from the neighbouring ZorA subunit. h, The effects of ZorA and ZorB mutations on EcZorI-mediated anti-phage defence against Bas24, as measured using EOP assays. Data are the mean of at least three replicates (datapoints indicate replicates) and are normalized to the control samples lacking EcZorI. ZorB(46–52>GGGSGGS), replacement of ZorB residues 46–52 with a GGGSGGS linker. Data for additional phages are provided in Extended Data Fig. 6a. i, Time-lapse phase-contrast microscopy analysis of E. coli cells expressing empty vector control or EcZorI with or without exposed to Bas24 at an MOI of 5 in the presence or absence of 30 µM CCCP. j, Quantification of the time-lapse microscopy images in i, displaying the measured cell area relative to the initial timepoint images. For j, data are mean ± s.d., derived from independent biological triplicates.