Membrane fusion activity of purified SipB, a Salmonella surface protein essential for mammalian cell invasion

An early event in Salmonella infection is the invasion of non‐phagocytic intestinal epithelial cells. The pathogen is taken up by macropinocytosis, induced by contact‐dependent delivery of bacterial proteins that subvert signalling pathways and promote cytoskeletal rearrangement. SipB, a Salmonella...

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Bibliographic Details
Published in:Molecular microbiology 2000-08, Vol.37 (4), p.727-739
Main Authors: Hayward, Richard D., McGhie, Emma J., Koronakis, Vassilis
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Bacterial Proteins - chemistry
Bacterial Proteins - metabolism
Bacterial Proteins - physiology
Escherichia coli
HeLa Cells
Humans
Hydrogen-Ion Concentration
macropinocytosis
membrane fusion
Membrane Fusion - physiology
Membrane Lipids - metabolism
Membrane Proteins - chemistry
Membrane Proteins - metabolism
Membrane Proteins - physiology
Molecular Sequence Data
Recombinant Proteins - chemistry
Recombinant Proteins - metabolism
Salmonella
Salmonella typhimurium - pathogenicity
SipB protein
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Summary:An early event in Salmonella infection is the invasion of non‐phagocytic intestinal epithelial cells. The pathogen is taken up by macropinocytosis, induced by contact‐dependent delivery of bacterial proteins that subvert signalling pathways and promote cytoskeletal rearrangement. SipB, a Salmonella protein required for delivery and invasion, was shown to localize to the cell surface of bacteria invading mammalian target cells and to fractionate with outer membrane proteins. To investigate the properties of SipB, we purified the native full‐length protein following expression in recombinant Escherichia coli. Purified SipB assembled into hexamers via an N‐terminal protease‐resistant domain predicted to form a trimeric coiled coil, reminiscent of viral envelope proteins that direct homotypic membrane fusion. The SipB protein integrated into both mammalian cell membranes and phospholipid vesicles without disturbing bilayer integrity, and it induced liposomal fusion that was optimal at neutral pH and influenced by membrane lipid composition. SipB directed heterotypic fusion, allowing delivery of contents from E. coli‐derived liposomes into the cytosol of living mammalian cells.
ISSN:0950-382X
1365-2958
DOI:10.1046/j.1365-2958.2000.02027.x