Abstract
We have isolated large amounts of E. coli outer-membrane protein A precursor (proOmpA). Purified proOmpA is active in membrane assembly, and this assembly is saturable with respect to the precursor protein. A proOmpA-Sepharose matrix allows affinity isolation of trigger factor, a soluble, 63,000 dalton monomeric protein that stabilizes proOmpA in assembly competent form. Comparison of trigger factor's amino-terminal sequence with those in a computer data bank and with those encoded by sec genes, as well as groEL and heat shock gene dnaK, suggests that trigger factor is encoded by a previously undescribed gene. Trigger factor and proOmpA form a 1:1 complex that can be isolated by gel filtration. Purified canine signal recognition particle (SRP) can also stabilize proOmpA for membrane insertion. This postribosomal activity of SRP suggests a unifying theme in protein translocation mechanisms.
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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Amino Acid Isomerases / isolation & purification
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Amino Acid Isomerases / physiology*
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Animals
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Bacterial Outer Membrane Proteins / isolation & purification
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Bacterial Outer Membrane Proteins / metabolism*
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Bacterial Proteins / isolation & purification
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Bacterial Proteins / physiology*
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Biological Transport
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Carrier Proteins / isolation & purification
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Carrier Proteins / physiology*
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Chromatography, Liquid
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Dogs
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Escherichia coli / metabolism*
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Escherichia coli Proteins*
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Membranes / metabolism
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Microsomes / metabolism
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Pancreas / metabolism
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Peptidylprolyl Isomerase
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Protein Binding
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Protein Precursors / isolation & purification
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Protein Precursors / metabolism*
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Ribonucleoproteins / pharmacology*
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Signal Recognition Particle
Substances
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Bacterial Outer Membrane Proteins
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Bacterial Proteins
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Carrier Proteins
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Escherichia coli Proteins
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Protein Precursors
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Ribonucleoproteins
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Signal Recognition Particle
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outer membrane protein A precursor (E coli)
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Amino Acid Isomerases
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Peptidylprolyl Isomerase