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NMR polypeptide backbone conformation of the E. coli outer membrane protein W.

ABSTRACT: The outer membrane proteins (Omps) are key factors for bacterial survival and virulence. Among the Omps that have been structurally characterized either by X-ray crystallography or by NMR in solution, the crystal structure of OmpW stands out because three of its four extracellular loops are well defined, whereas long extracellular loops in other E. coli Omps are disordered in the crystals as well as in NMR structures. OmpW thus presented an opportunity for a detailed comparison of the extracellular loops in a ?-barrel membrane protein structure in crystals and in noncrystalline milieus. Here, the polypeptide backbone conformation of OmpW in 30-Fos micelles was determined. Complete backbone NMR assignments were obtained and the loops were structurally characterized. In combination with the OmpW crystal structure, NMR line shape analyses, and (15)N{(1)H}-NOE data, these results showed that intact regular secondary structures in the loops undergo slow hinge motions at the detergent-solvent interface.

SUBMITTER: Horst R

PROVIDER: S-EPMC4150354 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

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NMR polypeptide backbone conformation of the E. coli outer membrane protein W.

Horst Reto R Stanczak Pawel P Wüthrich Kurt K

Structure (London, England : 1993) 20140710 8

The outer membrane proteins (Omps) are key factors for bacterial survival and virulence. Among the Omps that have been structurally characterized either by X-ray crystallography or by NMR in solution, the crystal structure of OmpW stands out because three of its four extracellular loops are well defined, whereas long extracellular loops in other E. coli Omps are disordered in the crystals as well as in NMR structures. OmpW thus presented an opportunity for a detailed comparison of the extracellu ...[more]

PMID: 25017731

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Project description:The human voltage dependent anion channel 1 (VDAC) is a 32 kDa ?-barrel integral membrane protein that controls the transport of ions across the outer mitochondrial membrane. Despite the determination of VDAC solution and diffraction structures, a structural basis for the mechanism of its function is not yet fully understood. Biophysical studies suggest VDAC requires a lipid bilayer to achieve full function, motivating the need for atomic resolution structural information of VDAC in a membrane environment. Here we report an essential step toward that goal: extensive assignments of backbone and side chain resonances for VDAC in DMPC lipid bilayers via magic angle spinning nuclear magnetic resonance (MAS NMR). VDAC reconstituted into DMPC lipid bilayers spontaneously forms two-dimensional lipid crystals, showing remarkable spectral resolution (0.5-0.3 ppm for (13)C line widths and <0.5 ppm (15)N line widths at 750 MHz). In addition to the benefits of working in a lipid bilayer, several distinct advantages are observed with the lipid crystalline preparation. First, the strong signals and sharp line widths facilitated extensive NMR resonance assignments for an integral membrane ?-barrel protein in lipid bilayers by MAS NMR. Second, a large number of residues in loop regions were readily observed and assigned, which can be challenging in detergent-solubilized membrane proteins where loop regions are often not detected due to line broadening from conformational exchange. Third, complete backbone and side chain chemical shift assignments could be obtained for the first 25 residues, which comprise the functionally important N-terminus. The reported assignments allow us to compare predicted torsion angles for VDAC prepared in DMPC 2D lipid crystals, DMPC liposomes, and LDAO-solubilized samples to address the possible effects of the membrane mimetic environment on the conformation of the protein. Concluding, we discuss the strengths and weaknesses of the reported assignment approach and the great potential for even more complete assignment studies and de novo structure determination via (1)H detected MAS NMR.

Dataset Information

NMR polypeptide backbone conformation of the E. coli outer membrane protein W.

Publications

NMR polypeptide backbone conformation of the E. coli outer membrane protein W.

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