2MQE

Solution structure of Escherichia coli Outer membrane protein A C-terminal domain

Summary for 2MQE

• Entry DOI: 10.2210/pdb2mqe/pdb
• NMR Information: BMRB: 25030
• Descriptor: OmpA domain protein transmembrane region-containing protein (1 entity in total)
• Functional Keywords: outer membrane protein a, ompa, membrane protein
• Biological source: Escherichia coli
• Total number of polymer chains: 1
• Total formula weight: 15712.67

Authors

Ishida, H.,Vogel, H. (deposition date: 2014-06-19, release date: 2014-09-03, Last modification date: 2023-06-14)

Primary citation

Ishida, H.,Garcia-Herrero, A.,Vogel, H.J.
The periplasmic domain of Escherichia coli outer membrane protein A can undergo a localized temperature dependent structural transition.
Biochim.Biophys.Acta, 1838:3014-3024, 2014

PubMed Abstract: Gram-negative bacteria such as Escherichia coli are surrounded by two membranes with a thin peptidoglycan (PG)-layer located in between them in the periplasmic space. The outer membrane protein A (OmpA) is a 325-residue protein and it is the major protein component of the outer membrane of E. coli. Previous structure determinations have focused on the N-terminal fragment (residues 1-171) of OmpA, which forms an eight stranded transmembrane β-barrel in the outer membrane. Consequently it was suggested that OmpA is composed of two independently folded domains in which the N-terminal β-barrel traverses the outer membrane and the C-terminal domain (residues 180-325) adopts a folded structure in the periplasmic space. However, some reports have proposed that full-length OmpA can instead refold in a temperature dependent manner into a single domain forming a larger transmembrane pore. Here, we have determined the NMR solution structure of the C-terminal periplasmic domain of E. coli OmpA (OmpA(180-325)). Our structure reveals that the C-terminal domain folds independently into a stable globular structure that is homologous to the previously reported PG-associated domain of Neisseria meningitides RmpM. Our results lend credence to the two domain structure model and a PG-binding function for OmpA, and we could indeed localize the PG-binding site on the protein through NMR chemical shift perturbation experiments. On the other hand, we found no evidence for binding of OmpA(180-325) with the TonB protein. In addition, we have also expressed and purified full-length OmpA (OmpA(1-325)) to study the structure of the full-length protein in micelles and nanodiscs by NMR spectroscopy. In both membrane mimetic environments, the recombinant OmpA maintains its two domain structure that is connected through a flexible linker. A series of temperature-dependent HSQC experiments and relaxation dispersion NMR experiments detected structural destabilization in the bulge region of the periplasmic domain of OmpA above physiological temperatures, which may induce dimerization and play a role in triggering the previously reported larger pore formation.

PubMed: 25135663
DOI: 10.1016/j.bbamem.2014.08.008

Experimental method

SOLUTION NMR