6s8n
Cryo-EM structure of LptB2FGC in complex with lipopolysaccharide
Structural highlights
FunctionLPTB_SHIFL Part of the ABC transporter complex LptBFG involved in the translocation of lipopolysaccharide (LPS) from the inner membrane to the outer membrane. Probably responsible for energy coupling to the transport system (By similarity). Publication Abstract from PubMedLipopolysaccharides (LPS) of Gram-negative bacteria are critical for the defence against cytotoxic substances and must be transported from the inner membrane (IM) to the outer membrane (OM) through a bridge formed by seven membrane proteins (LptBFGCADE). The IM component LptB2FG powers the process through a yet unclarified mechanism. Here we report three high-resolution cryo-EM structures of LptB2FG alone and complexed with LptC (LptB2FGC), trapped in either the LPS- or AMP-PNP-bound state. The structures reveal conformational changes between these states and substrate binding with or without LptC. We identify two functional transmembrane arginine-containing loops interacting with the bound AMP-PNP and elucidate allosteric communications between the domains. AMP-PNP binding induces an inward rotation and shift of the transmembrane helices of LptFG and LptC to tighten the cavity, with the closure of two lateral gates, to eventually expel LPS into the bridge. Functional assays reveal the functionality of the LptF and LptG periplasmic domains. Our findings shed light on the LPS transport mechanism. Cryo-EM structures of lipopolysaccharide transporter LptB2FGC in lipopolysaccharide or AMP-PNP-bound states reveal its transport mechanism.,Tang X, Chang S, Luo Q, Zhang Z, Qiao W, Xu C, Zhang C, Niu Y, Yang W, Wang T, Zhang Z, Zhu X, Wei X, Dong C, Zhang X, Dong H Nat Commun. 2019 Sep 13;10(1):4175. doi: 10.1038/s41467-019-11977-1. PMID:31519889[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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