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The C terminus of penicillin-binding protein 5 is essential for localisation to the E. coli inner membrane
Insights
Penicillin-binding protein 5 (PBP5) tightly binds the Escherichia coli inner membrane. Truncating its C terminus releases PBP5, indicating this region is crucial for membrane anchoring via an undescribed mechanism.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Penicillin-binding protein 5 (PBP5) is a known component of the Escherichia coli inner membrane.
- Previous studies identified PBP5 as an inner membrane protein.
Purpose of the Study:
- To investigate the specific regions of PBP5 responsible for its tight binding to the bacterial inner membrane.
- To elucidate the anchoring mechanism of PBP5.
Main Methods:
- Construction and analysis of a series of C-terminal deletion mutants of PBP5.
- Localization studies of wild-type and truncated PBP5 within Escherichia coli.
Main Results:
- Further evidence confirms PBP5 is tightly bound to the inner membrane.
- Deletion of as few as 10 amino acids from the C terminus causes PBP5 release into the periplasm.
- The C terminus is essential for membrane interaction, but lacks typical hydrophobic anchor sequences.
Conclusions:
- PBP5 utilizes a novel, non-hydrophobic mechanism for anchoring to the Escherichia coli inner membrane.
- The C terminus of PBP5 plays a critical role in its membrane association.
Abstract:
Penicillin-binding protein 5 (PBP5) has been previously identified as a component of the inner membrane of Escherichia coli and we present here further evidence that PBP5 is tightly bound to the membrane. To investigate the regions of PBP5 involved in membrane binding we have constructed a series of C-terminal deletions and shown that the removal of as few as 10 amino acids results in the release of the truncated protein into the periplasm. The C terminus, therefore, appears to be important for interaction with the membrane; however, inspection of the amino acid sequence does not reveal extended runs of hydrophobicity typical of a membrane anchor. Thus we conclude that PBP5 is anchored to the inner membrane by a mechanism not previously described.