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Folding-based suppression of extracytoplasmic toxicity conferred by processing-defective LamB
C L Cosma1, M D Crotwell, S Y Burrows
1Department of Molecular Biology, Princeton University, New Jersey 08544, USA.
Journal of Bacteriology
|June 11, 1998
Summary
Researchers identified a truncated TetA protein that corrects defects in maltoporin (LamB) processing and localization in Escherichia coli. This finding offers a novel mechanism for understanding protein trafficking in bacterial cell envelopes.
Area of Science:
- Bacterial cell envelope biogenesis
- Protein trafficking and localization
- Membrane protein processing
Background:
- Processing-defective maltoporin (LamB) mutants in Escherichia coli cause toxicity and altered outer membrane permeability.
- These mutants are tethered to the inner membrane due to inefficient signal peptidase cleavage.
Purpose of the Study:
- To characterize a multicopy suppressor of processing-defective LamB.
- To elucidate the mechanism by which this suppressor restores LamB localization to the outer membrane.
Main Methods:
- Utilized processing-defective LamB derivatives with signal peptidase cleavage site mutations.
- Employed cell fractionation and conformation-specific antibodies to assess protein localization.
- Analyzed suppressor plasmid DNA to identify the responsible gene product.
Main Results:
- A truncated TetA derivative (TetA') was identified as the multicopy suppressor.
- TetA' facilitates the folding and localization of processing-defective LamB precursors to the outer membrane.
- Suppression by TetA' is independent of the CpxA/CpxR and sigma E regulons.
Conclusions:
- TetA' mediates a novel mechanism for correcting LamB processing and trafficking defects.
- This discovery provides new insights into the regulation of protein localization within the bacterial cell envelope.