EC Number   |
General Information |
Reference |
|---|
  7.5.2.5 | evolution |
LptB2FG represents a third distinct type of ABC transporter, deemed type-III |
-, 750867 |
| 7.5.2.5 | evolution |
the Lpt system does not function in a completely conserved manner in all Gram-negative bacteria |
-, 751032 |
| 7.5.2.5 | malfunction |
mutations in the nucleotide-binding domain, LptB, of the transporter inactivates transporter function in vivo |
752031 |
| 7.5.2.5 | malfunction |
the C-term LptC mutation reduces the stability of the overall LptB2FGC complex, so increased LptB expression compensates by shifting the binding equilibrium in favor of the LptB2FG complex |
-, 750867 |
| 7.5.2.5 | malfunction |
the phenotypes of Neisseria meningitidis strains lacking LptB, LptC, LptH (EC 2.7.8.43), LptF, and LptG are identical to those lacking LptD or MsbA, i.e. the knockout mutants are viable but leaky and produce only very little LPS, which is not present at the cell surface |
-, 751032 |
| 7.5.2.5 | more |
identification of the specific subunit-to-subunit interactions that make the continuous transport of LPS from the cytoplasm to the exterior of the outer membrane by Lpt systems possible. The Lpt system is an oligomeric complex consisting of Lpt proteins A through G. The membrane-bound LptB, F, G and C subunits are connected to the LptD/E heterodimer in the OM by periplasmic LptA. LptB's catalytic activity couples to the LptF/G heterodimer's extraction of LPS like other ABC transporters, wherein the coupling helices of the TMD interact with the variable Q-loop of the NBD. Structural comparison of ATP-and ADP-bound LptB shows that ATP binding, hydrolysis and release induce conformational changes in the Q-loop region, mediated predominantly by two conserved residues (F90 and R91). LptC may be important to the efficient and stable assembly of the LptB2FG complex, in addition to directly transporting LPS |
750867 |
| 7.5.2.5 | more |
identification of the specific subunit-to-subunit interactions that make the continuous transport of LPS from the cytoplasm to the exterior of the outer membrane by Lpt systems possible. The Lpt system is an oligomeric complex consisting of Lpt proteins A through G. The membrane-bound LptB, F, G and C subunits are connected to the LptD/E heterodimer in the OM by periplasmic LptA. LptC may be important to the efficient and stable assembly of the LptB2FG complex, in addition to directly transporting LPS |
-, 750867 |
| 7.5.2.5 | more |
residue F90 is essential for proper formation of the Lpt inner membrane complex. crystal structures of LptB pre- and post-ATP hydrolysis suggest a role for an active site residue in phosphate exit. Residues E163, H195, and F90 of LptB are required for cell viability. E163 is essential for catalysis, through a bridging water molecule, this glutamate contacts the beta-phosphate of the nucleotide. ATP hydrolysis induces conformational changes. Conformational changes upon ATP hydrolysis show how reorganization of the active site causes changes in the region of LptB believed to interact with LptF/G. The dramatic movement of the switch region observed during ATP hydrolysis plays a critical role in communicating changes in the active site to changes in the transmembrane domains. The groove region of LptB is essential for interaction with inner membrane partners |
752031 |
| 7.5.2.5 | physiological function |
biosynthesis of lipopolysaccharide (LPS) in Gram-negative bacteria requires the transport of LPS to its destination, the outer leaflet of the outer membrane. In contrast to Escherichia coli, Neisseria meningitidis can survive without LPS and tolerates inactivation of genes involved in LPS synthesis and transport. LptA, LptB, LptC, LptE, LptF, and LptG proteins are not essential in Neisseria meningitidis and are not required for an essential process such as phospholipid transport. The LptD chaperone LptE is not directly involved in lipopolysaccharide transport in Neisseria meningitidis. LptC binds LPS |
-, 751032 |
| 7.5.2.5 | physiological function |
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 protein-bridge PEZ model, whereby a continuous stream of LPS molecules is pushed from subunit to subunit. The Lpt subunits form a continuous complex from the inner membrane (IM) to the OM and LPS is propelled along it continuously by the ATPase activity of LptB. Subunit-scale mechanisms of LPS transport include the novel ABC-like mechanism of the LptB2FG subcomplex and the lateral insertion of LPS into the OM by LptD/E, overview. 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. LPS is synthesized at the cytoplasmic side of the IM before it is transported to the OM. The LptB2FG tetramer extracts LPS from the outer leaflet of the IM and provides the energy to drive LPS transport through an ATPase-dependent mechanism, the LptB2FG complex drives LPS extraction from the IM to the periplasm |
-, 750867 |
