The outer membrane protein OmpW forms an eight-stranded β-barrel with a hydrophobic channel

Escherichia coli OmpW belongs to a family of small outer membrane proteins that are widespread in Gram-negative bacteria. Their functions are unknown, but recent data suggest that they may be involved in the protection of bacteria against various forms of environmental stress. To gain insight into the function of these proteins we have determined the crystal structure of E. coli OmpW to 2.7-angstrom resolution. The structure shows that OmpW forms an 8-stranded beta-barrel with a long and narrow hydrophobic channel that contains a bound n-dodecyl-N, N-dimethylamine-N-oxide detergent molecule. Single channel conductance experiments show that Omp W functions as an ion channel in planar lipid bilayers. The channel activity can be blocked by the addition of n-dodecyl-N, N-dimethylamine-N-oxide. Taken together, the data suggest that members of the Omp W family could be involved in the transport of small hydrophobic molecules across the bacterial outer membrane.