Lipid-protein interactions in DHPC micelles containing the integral membrane protein OmpX investigated by NMR spectroscopy.
Intermolecular nuclear Overhauser effects (NOEs) between the integral outer membrane protein OmpX from Escherichia coli and dihexanoylphosphatidylcholine (DHPC) provided a detailed description of protein-detergent interactions. The NOEs were measured in 3D (15)N- and (13)C-resolved [(1)H,(1)H]-NOESY spectra recorded with selectively methyl-protonated and otherwise uniformly (2)H,(13)C,(15)N-labeled OmpX in micelles of DHPC at natural isotope abundance. In these mixed micelles the NMR structure of OmpX consists of an eight-stranded antiparallel beta-barrel. The OmpX surface area covered with intermolecular NOEs to the DHPC hydrophobic tails forms a continuous cylinder jacket of approximately 28 A in height, which is centered about the middle of the long axis through the beta-barrel. In addition, some intermolecular NOEs with methyl groups of the DHPC polar head were identified along both boundaries of this cylinder jacket. The experimental data suggest that the hydrophobic surface areas of OmpX are covered with a monolayer of DHPC molecules, which appears to mimic quite faithfully the embedding of the beta-barrel in a double-layer lipid membrane.
Fernández
César
C
Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland.
Hilty
Christian
C
Wider
Gerhard
G
Wüthrich
Kurt
K
D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003902:Detergents; D029968:Escherichia coli Proteins / Q000737:chemistry*; D006867:Hydrolases; D057927:Hydrophobic and Hydrophilic Interactions; D008563:Membrane Lipids / Q000737:chemistry; D008823:Micelles; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010713:Phosphatidylcholines / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011522:Protons; D011994:Recombinant Proteins / Q000737:chemistry
D001425:Bacterial Outer Membrane Proteins; D003902:Detergents; D029968:Escherichia coli Proteins; D008563:Membrane Lipids; D008823:Micelles; D010713:Phosphatidylcholines; D011522:Protons; D011994:Recombinant Proteins; C482905:OmpX protein, E coli; C032166:1,2-hexanoylphosphatidylcholine; D006867:Hydrolases