Abstract
SummaryColicins kill Escherichia coli after translocation across the outer membrane. Colicin N displays an unusually simple translocation pathway, using the outer membrane protein F (OmpF) as both receptor and translocator. Studies of this binary complex may therefore reveal a significant component of the translocation pathway. Here we show that, in 2D crystals, colicin is found outside the porin trimer, suggesting that translocation may occur at the protein-lipid interface. The major lipid of the outer leaflet interface is lipopolysaccharide (LPS). It is further shown that colicin N binding displaces OmpF-bound LPS. The N-terminal helix of the pore-forming domain, which is not required for pore formation, rearranges and binds to OmpF. Colicin N also binds artificial OmpF dimers, indicating that trimeric symmetry plays no part in the interaction. The data indicate that colicin is closely associated with the OmpF-lipid interface, providing evidence that this peripheral pathway may play a role in colicin transmembrane transport.
Highlights
Univ Newcastle Upon Tyne, Inst Cell & Mol Biosci, Newcastle Upon Tyne NE2 4HH, Tyne & Wear, England; * Univ Sheffield, Dept Mol Biol & Biotechnol, Sheffield S10 2TN, S Yorkshire, England
In 2D crystals, colicin is found at the outside of the porin trimer suggesting that translocation may occur at the protein –lipid interface
The data indicate that the colicin is closely associated with the OmpFlipid interface and provide the first evidence that this peripheral pathway may play a role in colicin transmembrane transport
Summary
Univ Newcastle Upon Tyne, Inst Cell & Mol Biosci, Newcastle Upon Tyne NE2 4HH, Tyne & Wear, England; * Univ Sheffield, Dept Mol Biol & Biotechnol, Sheffield S10 2TN, S Yorkshire, England. Colicins kill Escherichia coli after translocation across the outer membrane and, for pore-forming colicin.
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