Structural Insights into the Lipid A Transport Pathway in MsbA

Area of Science:

• Structural Biology
• Microbiology
• Biochemistry

Background:

• MsbA is a crucial transporter in Gram-negative bacteria, responsible for moving lipid A and lipopolysaccharide across the inner membrane.
• Understanding MsbA's mechanism is vital for developing new antibacterial strategies.

Purpose of the Study:

• To elucidate the structural basis of MsbA's transport mechanism.
• To visualize the interaction of MsbA with its substrate, lipid A.

Main Methods:

• X-ray crystallography was employed to determine the structure of MsbA.
• Cocrystallization with lipid A and the use of a stabilizing facial amphiphile were key techniques.

Main Results:

• The study determined the 2.8-Å resolution X-ray structure of Salmonella typhimurium MsbA in an inward-facing conformation.
• A large opening in the transmembrane portal and putative lipid A density within the cavity and near the periplasmic surface were observed.

Conclusions:

• The determined structure provides novel insights into the lipid A transport pathway mediated by MsbA.
• The findings support a 'trap and flip' model for lipid A translocation across the inner membrane.