Cryo-EM structures of lipopolysaccharide transporter LptB₂FGC in lipopolysaccharide or AMP-PNP-bound states reveal its transport mechanism.

ABSTRACT: Lipopolysaccharides (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

SUBMITTER: Tang X 

PROVIDER: S-EPMC6744409 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature