Fig. 3. Zosurabalpin kills cells by inhibiting LptB₂FGC function.

a, Schematic of the trans-envelope lipopolysaccharide transporter. The inner-membrane complex LptB₂FGC is an ATP-binding cassette that uses ATP hydrolysis to extract LPS from the inner membrane and transport it to the cell surface. P_i, inorganic phosphate. b, In vitro assay monitoring the release of LPS from proteoliposomes containing LptB₂FGC complexes to LptA^I36pBPA–His7 by ultraviolet irradiation cross-linking and detection of LPS–LptA^I36pBPA–His7 adducts by LPS immunoblotting (Methods). The diagrams in a and b were created using BioRender. c, Zosurabalpin (ZAB) inhibits LPS transport in vitro by wild-type LptB₂FGC to LptA, whereas the structurally related inactive control compound RO7055137 (Fig. 1a) displays no LPS transport inhibition at comparable doses. Two amino acid substitutions, LptF(E249K) and LptF(I317N), that decreased the susceptibility of Acinetobacter to zosurabalpin were tested both individually and together. All three variants were resistant to compound treatment (Extended Data Table 6). Activity assays were conducted in biological triplicate, and representative blots are shown. UV, ultraviolet irradiation.