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Updated: May 17, 2026

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Published on: April 16, 2021
Bacterial lipids traverse the hydrophobic groove of TamB
1Research School of Biology, Australian National University, Canberra, ACT, Australia.
Abstract:
The double-membrane envelope of Gram-negative bacteria protects them against environmental stress and antibiotics. Phospholipids are a core component of the bacterial outer membrane (OM). However, how phospholipids are transported to the OM from the inner membrane where they are synthesized is poorly understood. We show that the AsmA-like protein TamB transfers lipids through a large hydrophobic groove that directly bridges the inner and outer membranes. Lipid dissociation at the outer membrane is impeded when TamB is bound to its OM partner protein TamA, but lipids can spontaneously enter the groove in simulations where the C terminus of TamB is embedded in the OM. Other members of the AsmA-like family in E. coli can also accommodate lipids within their hydrophobic grooves, suggesting they may also function as lipid transporters. Our findings highlight the lipid transport ability of TamB and other AsmA-like proteins, suggesting their importance in maintaining bacterial OM integrity.
Insights
The TamB protein transports phospholipids across bacterial membranes via a hydrophobic groove, crucial for maintaining outer membrane integrity. This discovery sheds light on essential lipid transport mechanisms in Gram-negative bacteria.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Gram-negative bacteria possess a double-membrane envelope essential for protection.
- Phospholipids are key components of the bacterial outer membrane (OM).
- Mechanisms of phospholipid transport from the inner membrane (IM) to the OM are not well understood.
Purpose of the Study:
- To investigate the role of the AsmA-like protein TamB in phospholipid transport.
- To elucidate the structural basis of lipid transfer across bacterial membranes.
Main Methods:
- Molecular simulations were used to model lipid transfer.
- Interactions between TamB, TamA, and phospholipids were analyzed.
- Structural analysis of AsmA-like proteins was performed.
Main Results:
- TamB facilitates lipid transfer through a hydrophobic groove connecting the IM and OM.
- Lipid release at the OM is regulated by TamA binding.
- Other AsmA-like proteins also possess lipid-accommodating grooves.
Conclusions:
- TamB is a key lipid transporter essential for OM integrity in Gram-negative bacteria.
- AsmA-like proteins represent a family of potential lipid transporters.
- Understanding these mechanisms is vital for combating bacterial infections.
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