Poster abstracts
Poster number 58 submitted by Brent Simpson
Elucidating how the LptB motor drives Lipopolysaccharide transport
Brent W. Simpson (Department of Microbiology), Rebecca M. Davis (Department of Microbiology), Alex Mestre (Department of Microbiology), Natividad Ruiz (Department of Microbiology)
Abstract:
Bacterial interactions with the environment are primarily mediated by the cell surface. To tightly control what enters the cell, many bacteria, the Gram-negatives, coat the cell surface with a highly impermeable lipid called lipopolysaccharide (LPS). This layer of LPS comprises the outer leaflet of the outer membrane and prevents toxic compounds, like antibiotics, from entering. After it is synthesized at the cytoplasmic membrane, LPS needs to be transported across the periplasm and the outer membrane to be assembled at the cell surface. This process is best studied in Escherichia coli which requires seven essential lpt (LPS transport) genes to encode the machinery. Here we explore the function of an unusual ATP-binding cassette (ABC) transporter, LptB2FG, that provides energy for LPS transport. The dimer of LptB utilizes the conserved features of ABC motor domains to hydrolyze ATP and cause conformational movements. These conformational changes are transmitted to transmembrane proteins LptFG to drive LPS transport. Utilizing structure-function and suppressor analyses, we have identified unique features of the ATPase LptB required for LPS transport. While LptB shares motifs with other members of the ABC transporter family for ATP binding and hydrolysis, it has a unique motif at its C-terminus that is essential for function. We demonstrate that the C-terminus of LptB functions with ATP-binding motifs in LptB and transmembrane regions of LptFG to coordinate ATP hydrolysis with LPS transport.
Keywords: Cell envelope, Lipopolysaccharide, Antibiotic resistance