7TPJ image
Entry Detail
PDB ID:
7TPJ
EMDB ID:
Title:
Single-Particle Cryo-EM Structure of the WaaL O-antigen ligase in its apo state
Biological Source:
Host Organism:
PDB Version:
Deposition Date:
2022-01-25
Release Date:
2022-04-06
Method Details:
Experimental Method:
Resolution:
3.46 Å
Aggregation State:
PARTICLE
Reconstruction Method:
SINGLE PARTICLE
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Putative cell surface polysaccharide polymerase/ligase
Chain IDs:A (auth: B)
Chain Length:413
Number of Molecules:1
Biological Source:Cupriavidus metallidurans
Polymer Type:polypeptide(L)
Description:Fab Heavy (H) Chain
Chain IDs:B (auth: H)
Chain Length:235
Number of Molecules:1
Biological Source:Homo sapiens
Polymer Type:polypeptide(L)
Description:Fab Light (L) Chain
Chain IDs:C (auth: L)
Chain Length:215
Number of Molecules:1
Biological Source:Homo sapiens
Ligand Molecules
Primary Citation

Abstact

The outer membrane of Gram-negative bacteria has an external leaflet that is largely composed of lipopolysaccharide, which provides a selective permeation barrier, particularly against antimicrobials1. The final and crucial step in the biosynthesis of lipopolysaccharide is the addition of a species-dependent O-antigen to the lipid A core oligosaccharide, which is catalysed by the O-antigen ligase WaaL2. Here we present structures of WaaL from Cupriavidus metallidurans, both in the apo state and in complex with its lipid carrier undecaprenyl pyrophosphate, determined by single-particle cryo-electron microscopy. The structures reveal that WaaL comprises 12 transmembrane helices and a predominantly α-helical periplasmic region, which we show contains many of the conserved residues that are required for catalysis. We observe a conserved fold within the GT-C family of glycosyltransferases and hypothesize that they have a common mechanism for shuttling the undecaprenyl-based carrier to and from the active site. The structures, combined with genetic, biochemical, bioinformatics and molecular dynamics simulation experiments, offer molecular details on how the ligands come in apposition, and allows us to propose a mechanistic model for catalysis. Together, our work provides a structural basis for lipopolysaccharide maturation in a member of the GT-C superfamily of glycosyltransferases.

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