6vci
Lipophilic envelope-spanning tunnel protein (LetB), domains MCE2-MCE3
Structural highlights
FunctionYEBT_ECOLI Component of a transport pathway that contributes to membrane integrity (PubMed:27795327). May directly span the intermembrane space, facilitating the transport of substrates across the periplasm (Probable).[1] [2] Publication Abstract from PubMedGram-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. References
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