Crystal structure of Acinetobacter baumannii CarO1

Experimental Data Snapshot

  • Resolution: 2.70 Å
  • R-Value Free: 0.278 
  • R-Value Work: 0.233 
  • R-Value Observed: 0.235 

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Small-Molecule Transport by CarO, an Abundant Eight-Stranded beta-Barrel Outer Membrane Protein from Acinetobacter baumannii.

Zahn, M.D'Agostino, T.Eren, E.Basle, A.Ceccarelli, M.van den Berg, B.

(2015) J Mol Biol 427: 2329-2339

  • DOI: https://doi.org/10.1016/j.jmb.2015.03.016
  • Primary Citation of Related Structures:  
    4RL9, 4RLB, 4RLC

  • PubMed Abstract: 

    Outer membrane (OM) β-barrel proteins composed of 12-18 β-strands mediate cellular entry of small molecules in Gram-negative bacteria. Small OM proteins with barrels of 10 strands or less are not known to transport small molecules. CarO (carbapenem-associated outer membrane protein) from Acinetobacter baumannii is a small OM protein that has been implicated in the uptake of ornithine and carbapenem antibiotics. Here we report crystal structures of three isoforms of CarO. The structures are very similar and show a monomeric eight-stranded barrel lacking an open channel. CarO has a substantial extracellular domain resembling a glove that contains all the divergent residues between the different isoforms. Liposome swelling experiments demonstrate that full-length CarO and a "loop-less" truncation mutant mediate small-molecule uptake at low levels but that they are unlikely to mediate passage of carbapenem antibiotics. These results are confirmed by biased molecular dynamics simulations that allowed us to quantitatively model the transport of selected small molecules.

  • Organizational Affiliation

    Institute for Cellular and Molecular Biosciences, The Medical School, Newcastle University, Newcastle upon Tyne, Tyne and Wear NE2 4HH, United Kingdom.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Carbapenem-associated resistance protein
A, B
255Acinetobacter baumanniiMutation(s): 0 
Gene Names: carO
Membrane Entity: Yes 
Find proteins for A6XB80 (Acinetobacter baumannii)
Explore A6XB80 
Go to UniProtKB:  A6XB80
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA6XB80
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.70 Å
  • R-Value Free: 0.278 
  • R-Value Work: 0.233 
  • R-Value Observed: 0.235 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 145.774α = 90
b = 63.26β = 119.7
c = 73.668γ = 90
Software Package:
Software NamePurpose
GDAdata collection
XDSdata reduction
XDSdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2015-04-22
    Type: Initial release
  • Version 1.1: 2015-06-24
    Changes: Database references
  • Version 1.2: 2024-02-28
    Changes: Data collection, Database references, Refinement description