4RLB

Crystal structure of Acinetobacter baumannii CarO2

Summary for 4RLB

• Entry DOI: 10.2210/pdb4rlb/pdb
• Related: 4FUV 4RL9 4RLC
• Descriptor: Carbapenem-associated resistance protein (1 entity in total)
• Functional Keywords: outer membrane protein, beta-barrel, membrane protein
• Biological source: Acinetobacter baumannii
• Total number of polymer chains: 2
• Total formula weight: 55238.73

Authors

Zahn, M.,Basle, A.,van den Berg, B. (deposition date: 2014-10-16, release date: 2015-04-22, Last modification date: 2024-02-28)

Primary citation

Zahn, M.,D'Agostino, T.,Eren, E.,Basle, A.,Ceccarelli, M.,van den Berg, B.
Small-Molecule Transport by CarO, an Abundant Eight-Stranded beta-Barrel Outer Membrane Protein from Acinetobacter baumannii.
J.Mol.Biol., 427:2329-2339, 2015

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.

PubMed: 25846137
DOI: 10.1016/j.jmb.2015.03.016

Experimental method

X-RAY DIFFRACTION (2.7 Å)