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Dynamic aspects of colicin N translocation through the Escherichia coli outer membrane
1UPR 9027, IBSM-IFR1, Centre National de la Recherche Scientifique, Marseille, France.
Abstract:
Colicin N is a bacteriocin that kills sensitive Escherichia coli cells. After binding to the cell surface-exposed receptor, a short period exists when a significant number of the cell-associated colicin N molecules are sensitive to external enzymes. Two colicin N populations are discriminated by proteases: the susceptible pool bound to OmpF porin on the cell surface and another population corresponding to protease-inaccessible colicin N. During translocation, colicin N reaches the periplasmic space and proteolytic cleavage of the colicin occurs only when the outer membrane barrier is permeabilized.
Insights
Colicin N, a bacteriocin, targets Escherichia coli. Protease sensitivity reveals two colicin N populations: one surface-bound and susceptible, the other inaccessible, indicating distinct translocation stages.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Colicin N is a bacteriocin toxic to Escherichia coli.
- Colicins utilize specific cell surface receptors for entry.
- The translocation process of colicins across bacterial membranes is complex.
Purpose of the Study:
- To investigate the different populations of cell-associated colicin N.
- To understand the role of proteases in discriminating colicin N states.
- To elucidate the timing of colicin N proteolytic cleavage during outer membrane translocation.
Main Methods:
- Enzyme sensitivity assays using proteases.
- Distinguishing colicin N populations based on protease accessibility.
- Monitoring colicin N translocation and cleavage.
Main Results:
- Two distinct colicin N populations were identified: protease-susceptible and protease-inaccessible.
- The susceptible population is bound to the OmpF porin receptor on the cell surface.
- Proteolytic cleavage of colicin N occurs only after the outer membrane barrier is compromised during translocation.
Conclusions:
- Protease sensitivity serves as a marker for colicin N translocation stages.
- The OmpF porin is involved in the initial cell surface association of colicin N.
- Colicin N translocation involves a transient state of protease sensitivity before periplasmic entry.