Solution NMR mapping of water-accessible residues in the transmembrane beta-barrel of OmpX.
The atomic structure of OmpX, the smallest member of the bacterial outer membrane protein family, has been previously established by X-ray crystallography and NMR spectroscopy. In apparent conflict with electrophysiological studies, the lumen of its transmembrane beta-barrel appears too tightly packed with amino acid side chains to let any solute flow through. In the present study, high-resolution solution NMR spectra were obtained of OmpX kept water-soluble by either amphipol A8-35 or the detergent dihexanoylphosphatidylcholine. Hydrogen/deuterium exchange measurements performed after prolonged equilibration show that, whatever the surfactant used, some of the amide protons of the membrane-spanning region exchange much more readily than others, which likely reflects the dynamics of the barrel.
Catoire
Laurent J
LJ
Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, CNRS/Université Paris-7, Institut de Biologie Physico-Chimique (FRC 550), 75005 Paris, France. laurent.catoire@ibpc.fr
Zoonens
Manuela
M
van Heijenoort
Carine
C
Giusti
Fabrice
F
Guittet
Eric
E
Popot
Jean-Luc
JL
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D002462:Cell Membrane; D003902:Detergents / Q000737:chemistry; D041961:Deuterium Exchange Measurement; D029968:Escherichia coli Proteins / Q000737:chemistry*; D006867:Hydrolases / Q000737:chemistry*; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010713:Phosphatidylcholines / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011437:Propylamines / Q000737:chemistry; D017433:Protein Structure, Secondary; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry*
D001425:Bacterial Outer Membrane Proteins; D003902:Detergents; D029968:Escherichia coli Proteins; D010713:Phosphatidylcholines; D011108:Polymers; D011437:Propylamines; D012997:Solvents; C499017:amphipol A8-35; D014867:Water; C482905:OmpX protein, E coli; C032166:1,2-hexanoylphosphatidylcholine; D006867:Hydrolases