Cytoplasmic ATP Hydrolysis Powers Transport of Lipopolysaccharide Across the Periplasm in E. coli

Powering LPS Export The surface of Gram-negative bacteria such as Escherichia coli is covered in lipopolysaccharide (LPS), which must be synthesized within the cytoplasm and then exported across the periplasm to the outer leaflet of the outer membrane. Okuda et al. (p. 1214 , published online 8 November) describe the detection of LPS molecules bound to specific components of the E. coli lipopolysaccharide exporter during transport in vivo. In vitro reconstitution of LPS transport revealed the energetic requirements for the first two steps of transport, release from the membrane and transit along the periplasmic bridge of the exporter that connects the inner and outer membrane components. The findings suggest that adenosine triphosphate hydrolysis by a cytoplasmic component of the machine provides energy to push a continuous stream of LPS against its concentration gradient to the cell surface.