Structure of an essential inner membrane protein-LPS complex identifies a novel anti-microbial peptide

ABSTRACT: Lipopolysaccharide (LPS) resides in the outer membrane (OM) of Gram-negative bacteria where it is responsible for barrier function and immune modulation. LPS is the target of polymyxins, last-resort antibiotics whose clinical use is threatened by increasing resistance. Steps in LPS biogenesis are known, but how LPS biosynthesis and transport to the OM is coordinated remains poorly understood. Here, we find that depletion of the Escherichia coli inner membrane protein PbgA attenuates pathogenesis and produces defects in the OM. Structural analysis of PbgA identifies an enzyme superfamily known to modify the envelopes of Gram-positive and Gram-negative bacteria; however, PbgA reveals a defunct hydrolase-active site, a distinctive architecture, and an unprecedented lipid A-binding motif along the periplasmic leaflet of the inner membrane. Unlike canonical lipid-binding proteins, PbgA achieves LPS coordination primarily through backbone-mediated interactions. Offensive mutations within the lipid A-binding motif disrupt the OM barrier, suggesting that LPS perception by PbgA plays a key role in maintaining OM homeostasis. PbgA-derived synthetic peptides selectively bind to LPS in vitro and inhibit the growth of diverse Gram-negative bacterial species, including polymyxin-resistant strains. Our studies uncover an essential pseudo-hydrolase with an unexpected link to OM biogenesis, highlight a new structural paradigm in selective lipid recognition, and provide important templates for future antibiotic discovery.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Escherichia Coli K-12 (ncbitaxon:83333)

SUBMITTER: erik verschueren  

PROVIDER: MSV000083754 | MassIVE | Wed May 08 14:46:00 BST 2019

REPOSITORIES: MassIVE