Ligand-Mediated Folding of the OmpA Periplasmic Domain from Acinetobacter baumannii

The periplasmic domain of OmpA from Acinetobacter baumannii (AbOmpA-PD) binds to diaminopimelate and anchors the outer membrane to the peptidoglycan layer in the cell wall. Although the crystal structure of AbOmpA-PD with its ligands has been reported, the mechanism of ligand-mediated folding of AbO...

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Bibliographic Details
Published in:Biophysical journal 2017-05, Vol.112 (10), p.2089-2098
Main Authors: Mushtaq, Ameeq Ul, Park, Jeong Soon, Bae, Sung-Hun, Kim, Hye-Yeon, Yeo, Kwon Joo, Hwang, Eunha, Lee, Ki Yong, Jee, Jun-Goo, Cheong, Hae-Kap, Jeon, Young Ho
Format: Article
Language:English
Subjects:
Acinetobacter baumannii
Amino Acid Sequence
Bacterial Outer Membrane Proteins - chemistry
Bacterial Outer Membrane Proteins - genetics
Bacterial Outer Membrane Proteins - metabolism
Binding sites
Cell walls
Chromatography, Gel
Circular Dichroism
Crystal structure
Dispersion
Dynamic structural analysis
Escherichia coli
Fluorometry
Folding
Glycine
Glycine - chemistry
Glycine - metabolism
Gram-negative bacteria
In vitro methods and tests
Ligands
Molecular Dynamics Simulation
Monte Carlo Method
Nuclear Magnetic Resonance, Biomolecular
Peptidoglycans
Protein Binding
Protein Domains
Protein Folding
Proteins
Solutions
Structural members
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Summary:The periplasmic domain of OmpA from Acinetobacter baumannii (AbOmpA-PD) binds to diaminopimelate and anchors the outer membrane to the peptidoglycan layer in the cell wall. Although the crystal structure of AbOmpA-PD with its ligands has been reported, the mechanism of ligand-mediated folding of AbOmpA remains elusive. Here, we report that in vitro refolded apo-AbOmpA-PD in the absence of ligand exists as a mixture of two partially folded forms in solution: mostly unfolded (apo-state I) and hololike (apo-state II) states. Binding of the diaminopimelate or glycine ligand induced complete folding of AbOmpA-PD. The apo-state I was highly flexible and contained some secondary structural elements, whereas the apo-state II closely resembled the holo-state in terms of both structure and backbone dynamics, except for the ligand-binding region. 15N-relaxation-dispersion analyses for apo-state II revealed substantial motion on a millisecond timescale of residues in the H3 helix near the ligand-binding site, with this motion disappearing upon ligand binding. These results provide an insight into the ligand-mediated folding mechanism of AbOmpA-PD in solution.
ISSN:0006-3495
1542-0086
DOI:10.1016/j.bpj.2017.04.015