Poster abstracts
Poster number 32 submitted by Emily Lundstedt
How LPS structure affects its transport by LptB2FG
Emily Lundstedt (Department of Microbiology), Rebecca Davis (Department of Microbiology), Natividad Ruiz (Department of Microbiology)
Abstract:
The cell envelope is what defines a bacterium from its environment and protects it from the outside world. Gram-negative bacteria are diderms, and thus have a cell envelope composed of both an inner membrane and an outer membrane. The outermost leaflet of the outer membrane is made up of lipopolysaccharide (LPS). Tight packing of LPS molecules makes the outer membrane a potent permeability barrier, protecting the cell from entry of harmful compounds such as antibiotics. LPS is synthesized at the inner membrane and is transported to the outer leaflet of the outer membrane by the LPS transport (Lpt) machinery. The movement of LPS through this machinery is powered by the ATP-binding cassette (ABC) transporter LptB2FG. Although it is clear that ATP hydrolysis is required for LPS transport, it is not known how the ATP-hydrolysis cycle is coupled to the extraction of LPS. To elucidate this mechanism, we performed structure-function analysis of mutants that alter residues along the interaction interface between the ATPase subunits LptB2 and transmembrane subunits LptFG. We identified a new essential residue within LptB that is critical for connecting ATP hydrolysis and LPS transport. The lethality of a mutation that alters this residue in LptB could be suppressed by deletion of an LPS biosynthesis gene, lpxM. Since the loss of LpxM results in an altered LPS structure, these findings suggest that this residue in LptB is responsible for conferring conformational changes associated with ATP hydrolysis to drive transport of LPS by lptFG.
Keywords: Antibiotic resistance, Cell envelope, Lipopolysaccharide