Abstract
SecA, an essential component of the general protein secretion pathway of bacteria, is present in Escherichia coli as soluble and membrane-integral forms. Here we show by electron microscopy that SecA assumes two characteristic forms in the presence of phospholipid monolayers: dumbbell-shaped elongated structures and ring-like pore structures. The ring-like pore structures with diameters of 8 nm and holes of 2 nm are found only in the presence of anionic phospholipids. These ring-like pore structures with larger 3- to 6-nm holes (without staining) were also observed by atomic force microscopic examination. They do not form in solution or in the presence of uncharged phosphatidylcholine. These ring-like phospholipid-induced pore-structures may form the core of bacterial protein-conducting channels through bacterial membranes.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenosine Triphosphatases / chemistry*
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Adenosine Triphosphatases / isolation & purification
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Adenosine Triphosphatases / ultrastructure
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Bacterial Proteins*
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Escherichia coli / physiology*
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Escherichia coli / ultrastructure
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Escherichia coli Proteins / chemistry*
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Escherichia coli Proteins / isolation & purification
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Escherichia coli Proteins / ultrastructure
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Ion Channels / chemistry
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Liposomes
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Membrane Transport Proteins / chemistry*
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Membrane Transport Proteins / isolation & purification
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Membrane Transport Proteins / ultrastructure
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Microscopy, Atomic Force
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Microscopy, Electron
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Phospholipids / chemistry
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Protein Conformation
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SEC Translocation Channels
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SecA Proteins
Substances
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Bacterial Proteins
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Escherichia coli Proteins
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Ion Channels
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Liposomes
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Membrane Transport Proteins
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Phospholipids
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SEC Translocation Channels
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Adenosine Triphosphatases
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SecA Proteins