Abstract
Gram-negative bacteria have a dense outer membrane (OM) coating of lipopolysaccharides, which is essential to their survival. This coating is assembled by the LPS (lipopolysaccharide) transport (Lpt) system, a coordinated seven-subunit protein complex that spans the cellular envelope. LPS transport is driven by an ATPase-dependent mechanism dubbed the “PEZ” model, whereby a continuous stream of LPS molecules is pushed from subunit to subunit. This review explores recent structural and functional findings that have elucidated the subunit-scale mechanisms of LPS transport, including the novel ABC-like mechanism of the LptB2FG subcomplex and the lateral insertion of LPS into the OM by LptD/E. New questions are also raised about the functional significance of LptA oligomerization and LptC. The tightly regulated interactions between these connected subcomplexes suggest a pathway that can react dynamically to membrane stress and may prove to be a valuable target for new antibiotic therapies for Gram-negative pathogens.
Highlights
Gram-negative bacteria protect themselves from chemical stressors by incorporating hydrophobic lipopolysaccharide (LPS) into their outer membranes
The LPS coating is critical to the integrity of the cellular envelope, and Gram-negative bacteria need to replenish it at an astonishing rate to survive
LPS is synthesized at the cytoplasmic side of the inner membrane (IM) before it is transported to the outer membrane (OM)
Summary
Gram-negative bacteria protect themselves from chemical stressors by incorporating hydrophobic lipopolysaccharide (LPS) into their outer membranes. 2018, 19, x FOR PEER REVIEW the individual interactions between the Lpt subunits and the structural features of the Gram-negative the IM to the OM and LPS is propelled along it continuously by the ATPase activity of LptB has long cellular envelope, but direct evidence of the complete bridge and its activity was not observed until been favoured over the periplasmic dissolution or membrane-junction models. Sci. 2018, 19, x FOR PEER REVIEW the individual interactions between the Lpt subunits and the structural features of the Gram-negative the IM to the OM and LPS is propelled along it continuously by the ATPase activity of LptB has long cellular envelope, but direct evidence of the complete bridge and its activity was not observed until been favoured over the periplasmic dissolution or membrane-junction models It is consistent with a recent where. The current researchfunction on the structural interactions within the Lpt system and discuss their potential implications regarding function and regulation of OM biogenesis overall
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