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Publication Abstract from PubMed

Gram-negative bacteria are surrounded by an outer membrane composed of phospholipids and lipopolysaccharide, which acts as a barrier and contributes to antibiotic resistance. The systems that mediate phospholipid trafficking across the periplasm, such as MCE (Mammalian Cell Entry) transporters, have not been well characterized. Our ~3.5 A cryo-EM structure of the E. coli MCE protein LetB reveals an ~0.6 megadalton complex that consists of seven stacked rings, with a central hydrophobic tunnel sufficiently long to span the periplasm. Lipids bind inside the tunnel, suggesting that it functions as a pathway for lipid transport. Cryo-EM structures in the open and closed states reveal a dynamic tunnel lining, with implications for gating or substrate translocation. Our results support a model in which LetB establishes a physical link between the two membranes and creates a hydrophobic pathway for the translocation of lipids across the periplasm.

LetB Structure Reveals a Tunnel for Lipid Transport across the Bacterial Envelope.,Isom GL, Coudray N, MacRae MR, McManus CT, Ekiert DC, Bhabha G Cell. 2020 Apr 30;181(3):653-664.e19. doi: 10.1016/j.cell.2020.03.030. PMID:32359438^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.