Sec-independent translocation of a 100-residue periplasmic N-terminal tail in the E. coli inner membrane protein proW

EMBO J. 1994 Oct 3;13(19):4653-61.


The ProW protein, located in the inner membrane of Escherichia coli, has a very unusual topology with a 100-residue-long N-terminal tail protruding into the periplasmic space. We have studied the mechanism of membrane translocation of the periplasmic tail by analysing ProW-PhoA and ProW-Lep fusion proteins, both in wild-type cells and in cells with an impaired sec machinery. Our results show that the translocation efficiency is not affected by treatments that compromise the SecA and SecY functions, but that translocation is completely blocked by dissipation of the proton motive force or by the introduction of extra positively charged residues into the N-terminal tail. This suggests that the sec machinery can act properly only on domains located on the C-terminal side of a translocation signal, and that the N-terminal tail is driven through the membrane by a mechanism that involves the proton motive force.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters*
  • Adenosine Triphosphatases / physiology*
  • Amino Acid Sequence
  • Bacterial Proteins / metabolism*
  • Bacterial Proteins / physiology*
  • Base Sequence
  • Biological Transport / physiology
  • Biological Transport, Active / physiology
  • Carrier Proteins / metabolism
  • Electrophysiology
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Maltose-Binding Proteins
  • Membrane Proteins / metabolism*
  • Membrane Transport Proteins*
  • Molecular Sequence Data
  • Monosaccharide Transport Proteins*
  • Periplasmic Binding Proteins*
  • Protein Sorting Signals / physiology
  • Protons
  • Recombinant Fusion Proteins / metabolism
  • SEC Translocation Channels
  • SecA Proteins
  • Structure-Activity Relationship


  • ATP-Binding Cassette Transporters
  • Bacterial Proteins
  • Carrier Proteins
  • Escherichia coli Proteins
  • MalE protein, E coli
  • Maltose-Binding Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • Monosaccharide Transport Proteins
  • Periplasmic Binding Proteins
  • ProW protein, E coli
  • Protein Sorting Signals
  • Protons
  • Recombinant Fusion Proteins
  • SEC Translocation Channels
  • SecB protein, Bacteria
  • SecY protein, E coli
  • maltose transport system, E coli
  • Adenosine Triphosphatases
  • SecA Proteins