ProOmpA spontaneously folds in a membrane assembly competent state which trigger factor stabilizes

The precursor protein proOmpA can translocate across purified Escherichia coli inner membrane vesicles in the absence of any other soluble proteins. ProOmpA, purified 2000‐fold in the presence of 8 M urea, is competent for translocation following rapid renaturation via dilution. ATP, the transmembra...

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Bibliographic Details
Published in:The EMBO journal 1988-06, Vol.7 (6), p.1831-1835
Main Authors: Crooke, E., Brundage, L., Rice, M., Wickner, W.
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Bacterial Outer Membrane Proteins - metabolism
Bacterial Proteins - metabolism
Bacteriology
Biogenesis of cell structures, supramolecular organization
Biological and medical sciences
Biological Transport
Cell Membrane - metabolism
Escherichia coli
Escherichia coli - metabolism
Fundamental and applied biological sciences. Psychology
inner membranes
Microbiology
Protein Conformation
Protein Precursors - metabolism
Protein Processing, Post-Translational
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Summary:The precursor protein proOmpA can translocate across purified Escherichia coli inner membrane vesicles in the absence of any other soluble proteins. ProOmpA, purified 2000‐fold in the presence of 8 M urea, is competent for translocation following rapid renaturation via dilution. ATP, the transmembrane electrochemical potential, and functional secY protein are essential for the translocation of proOmpA renatured by dilution. The kinetics of its translocation and the level of translocation at each concentration of ATP are indistinguishable from that of proOmpA renatured by dialysis with trigger factor. After dilution, the proOmpA rapidly loses its competence for membrane assembly. However, this competence is stabilized by trigger factor. Assembly‐competent proOmpA is in a protease‐sensitive conformation, whereas proOmpA which has lost this competence is more resistant to degradation. This suggests that the primary role for trigger factor in in vitro protein translocation is to maintain precursor proteins in a translocation‐competent conformation. We propose that a properly folded precursor protein and ATP are the only soluble components which are essential for bacterial protein translocation.
ISSN:0261-4189
1460-2075
DOI:10.1002/j.1460-2075.1988.tb03015.x