FIG 1.

LPS transport system. (A) Chemical structure of LPS. The lipid A and core structures depicted correspond to those of E. coli K-12. The O antigen, if present, is highly variable. Gal, d-galactose; Glc, d-glucose; Hep, l-glycero-d-manno-heptose; KDO, 2-keto-3-deoxy-octonic acid; EtN, ethanolamine; P, phosphate. (B) Transport of LPS from IM to OM. After flipping over the IM by MsbA protein, LPS is transported across the periplasm and assembled at the cell surface by the Lpt machinery. (C) Graphic representation of the crystal structure of E. coli LptA (Protein Data Bank [PDB] 2r19, chain B). Residues involved in LptC interaction according to reference 55 (I38, E39, S40, Q42, and Q43) are represented by red spheres; residues involved in LPS interaction according to reference 21 (T32, F95, Y114, and L116) are represented by blue spheres. Residue I36 is involved in both LPS and LptC interactions and is represented in pink.