5NUO

Structural basis for maintenance of bacterial outer membrane lipid asymmetry


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.2 Å
  • R-Value Free: 0.269 
  • R-Value Work: 0.223 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Structural basis for maintenance of bacterial outer membrane lipid asymmetry.

Abellon-Ruiz, J.Kaptan, S.S.Basle, A.Claudi, B.Bumann, D.Kleinekathofer, U.van den Berg, B.

(2017) Nat Microbiol 2: 1616-1623

  • DOI: 10.1038/s41564-017-0046-x
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • The Gram-negative bacterial outer membrane (OM) is a unique bilayer that forms an efficient permeation barrier to protect the cell from noxious compounds 1,2 . The defining characteristic of the OM is lipid asymmetry, with phospholipids comprising th ...

    The Gram-negative bacterial outer membrane (OM) is a unique bilayer that forms an efficient permeation barrier to protect the cell from noxious compounds 1,2 . The defining characteristic of the OM is lipid asymmetry, with phospholipids comprising the inner leaflet and lipopolysaccharides comprising the outer leaflet 1-3 . This asymmetry is maintained by the Mla pathway, a six-component system that is widespread in Gram-negative bacteria and is thought to mediate retrograde transport of misplaced phospholipids from the outer leaflet of the OM to the cytoplasmic membrane 4 . The OM lipoprotein MlaA performs the first step in this process via an unknown mechanism that does not require external energy input. Here we show, using X-ray crystallography, molecular dynamics simulations and in vitro and in vivo functional assays, that MlaA is a monomeric α-helical OM protein that functions as a phospholipid translocation channel, forming a ~20-Å-thick doughnut embedded in the inner leaflet of the OM with a central, amphipathic pore. This architecture prevents access of inner leaflet phospholipids to the pore, but allows outer leaflet phospholipids to bind to a pronounced ridge surrounding the channel, followed by diffusion towards the periplasmic space. Enterobacterial MlaA proteins form stable complexes with OmpF/C 5,6 , but the porins do not appear to play an active role in phospholipid transport. MlaA represents a lipid transport protein that selectively removes outer leaflet phospholipids to help maintain the essential barrier function of the bacterial OM.


    Organizational Affiliation

    Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Outer membrane protein F
C, A, E
340Escherichia coli (strain K12)Mutation(s): 0 
Gene Names: ompF (cmlB, coa, cry, tolF)
Membrane protein
mpstruct
Group: 
TRANSMEMBRANE PROTEINS: ALPHA-HELICAL
Sub Group: 
Outer Membrane Proteins
Protein: 
MlaA lipid transport protein in complex with OmpF
Find proteins for P02931 (Escherichia coli (strain K12))
Go to UniProtKB:  P02931
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
ABC transporter permease
D, B, F
236Klebsiella pneumoniaeMutation(s): 0 
Gene Names: mlaA (mlaA_2, vacJ)
Membrane protein
mpstruct
Group: 
TRANSMEMBRANE PROTEINS: ALPHA-HELICAL
Sub Group: 
Outer Membrane Proteins
Protein: 
MlaA lipid transport protein in complex with OmpF
Find proteins for A0A0W8AQT6 (Klebsiella pneumoniae)
Go to UniProtKB:  A0A0W8AQT6
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
SO4
Query on SO4

Download SDF File 
Download CCD File 
A, C, E
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
C8E
Query on C8E

Download SDF File 
Download CCD File 
A, B, C, D, E, F
(HYDROXYETHYLOXY)TRI(ETHYLOXY)OCTANE
C16 H34 O5
FEOZZFHAVXYAMB-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.2 Å
  • R-Value Free: 0.269 
  • R-Value Work: 0.223 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 95.597α = 90.00
b = 146.461β = 90.00
c = 234.931γ = 90.00
Software Package:
Software NamePurpose
PHENIXrefinement
Aimlessdata scaling
xia2data reduction
Cootmodel building
RESOLVEmodel building
PHASERphasing
DIALSdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History & Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
European UnionUnited Kingdom115525

Revision History 

  • Version 1.0: 2017-10-25
    Type: Initial release
  • Version 1.1: 2017-11-01
    Type: Database references
  • Version 1.2: 2017-12-06
    Type: Database references