prlA Suppressors in Escherichia coli Relieve the Proton Electrochemical Gradient Dependency of Translocation of Wild-Type Precursors

The SecY protein of Escherichia coli is an integral membrane component of the protein export apparatus. Suppressor mutations in the secY gene (prlA alleles) have been isolated that restore the secretion of precursor proteins with defective signal sequences. These mutations have never been shown to a...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1996-06, Vol.93 (12), p.5953-5957
Main Authors: Nouwen, Nico, De Kruijff, Ben, Tommassen, Jan
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Azides
Bacteria
Bacterial Outer Membrane Proteins - metabolism
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Biological Transport
Carbonyl Cyanide m-Chlorophenyl Hydrazone - pharmacology
Electrochemistry
Escherichia coli
Escherichia coli - metabolism
Escherichia coli Proteins
Genes, Suppressor
Genetic mutation
Genetic suppression
Kinetics
Molecular biology
Mutation
Noise reduction
Plasmids
Protein precursors
Protein Precursors - metabolism
Protein Sorting Signals - metabolism
Protein transport
Proteins
SEC Translocation Channels
Sodium
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Summary:The SecY protein of Escherichia coli is an integral membrane component of the protein export apparatus. Suppressor mutations in the secY gene (prlA alleles) have been isolated that restore the secretion of precursor proteins with defective signal sequences. These mutations have never been shown to affect the translocation of wild-type precursor proteins. Here, we report that prlA suppressor mutations relieve the proton-motive force (pmf) dependency of the translocation of wild-type precursors, both in vivo and in vitro. Furthermore, the proton-motive force dependency of the translocation of a precursor with a stably folded domain in the mature region was suppressed by prlA mutations in vitro. These data show that prlA mutations cause a general relaxation of the export apparatus rather than a specific change that results in bypassing of the recognition of the signal sequence. In addition, these results are indicative for a mechanism in which the proton-motive force stimulates translocation by altering the conformation of the translocon.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.93.12.5953