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Structure of E. coli MCE protein MlaD, periplasmic domainStructure of E. coli MCE protein MlaD, periplasmic domain
Structural highlights
FunctionMLAD_ECO57 Part of the ABC transporter complex MlaFEDB that actively prevents phospholipid accumulation at the cell surface. Probably maintains lipid asymmetry in the outer membrane by retrograde trafficking of phospholipids from the outer membrane to the inner membrane.[UniProtKB:P64604] Publication Abstract from PubMedHow phospholipids are trafficked between the bacterial inner and outer membranes through the hydrophilic space of the periplasm is not known. We report that members of the mammalian cell entry (MCE) protein family form hexameric assemblies with a central channel capable of mediating lipid transport. The E. coli MCE protein, MlaD, forms a ring associated with an ABC transporter complex in the inner membrane. A soluble lipid-binding protein, MlaC, ferries lipids between MlaD and an outer membrane protein complex. In contrast, EM structures of two other E. coli MCE proteins show that YebT forms an elongated tube consisting of seven stacked MCE rings, and PqiB adopts a syringe-like architecture. Both YebT and PqiB create channels of sufficient length to span the periplasmic space. This work reveals diverse architectures of highly conserved protein-based channels implicated in the transport of lipids between the membranes of bacteria and some eukaryotic organelles. Architectures of Lipid Transport Systems for the Bacterial Outer Membrane.,Ekiert DC, Bhabha G, Isom GL, Greenan G, Ovchinnikov S, Henderson IR, Cox JS, Vale RD Cell. 2017 Apr 6;169(2):273-285.e17. doi: 10.1016/j.cell.2017.03.019. PMID:28388411[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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