Download MendeleyStructural basis of lipopolysaccharide extraction by the LptB2FGC complex.
Li, Y., Orlando, B.J., Liao, M.(2019) Nature 567: 486-490
- PubMed: 30894744
- DOI: https://doi.org/10.1038/s41586-019-1025-6
- Primary Citation of Related Structures:
6MHU, 6MHZ, 6MI7, 6MI8 - PubMed Abstract:
In Gram-negative bacteria, lipopolysaccharide is essential for outer membrane formation and antibiotic resistance. The seven lipopolysaccharide transport (Lpt) proteins A-G move lipopolysaccharide from the inner to the outer membrane. The ATP-binding cassette transporter LptB 2 FG, which tightly associates with LptC, extracts lipopolysaccharide out of the inner membrane. The mechanism of the LptB 2 FG-LptC complex (LptB 2 FGC) and the role of LptC in lipopolysaccharide transport are poorly understood. Here we characterize the structures of LptB 2 FG and LptB 2 FGC in nucleotide-free and vanadate-trapped states, using single-particle cryo-electron microscopy. These structures resolve the bound lipopolysaccharide, reveal transporter-lipopolysaccharide interactions with side-chain details and uncover how the capture and extrusion of lipopolysaccharide are coupled to conformational rearrangements of LptB 2 FGC. LptC inserts its transmembrane helix between the two transmembrane domains of LptB 2 FG, which represents a previously unknown regulatory mechanism for ATP-binding cassette transporters. Our results suggest a role for LptC in achieving efficient lipopolysaccharide transport, by coordinating the action of LptB 2 FG in the inner membrane and Lpt protein interactions in the periplasm.
Organizational Affiliation:
Department of Cell Biology, Harvard Medical School, Boston, MA, USA.
