Inversion of the membrane topology of SecG coupled with SecA-dependent preprotein translocation

Cell. 1996 Apr 5;85(1):71-81. doi: 10.1016/s0092-8674(00)81083-1.


E. coli preprotein translocase comprises SecA and SecY/E/G complex. SecA delivers the preprotein to the putative protein-conducting channel formed by SecY/E by undergoing ATP-driven cycles of membrane insertion and deinsertion. SecG renders the translocase highly efficient. An antibody raised against the C-terminal region of SecG inhibits preprotein translocation into everted membrane vesicles despite the exposure of this region to the inside of membrane vesicles in the absence of preprotein translocation. When preprotein translocation was started with ATP and then blocked by the inhibition of ATP hydrolysis, the C-terminal region was exposed to the outside of membrane vesicles. Another region of SecG showed a change in membrane sidedness upon preprotein translocation, indicating that SecG undergoes topology inversion. This topology inversion was tightly coupled to the SecG function and linked with the insertion-deinsertion cycle of SecA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / metabolism*
  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / immunology
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Biological Transport / physiology
  • Cytoplasm / metabolism
  • Cytoplasm / ultrastructure
  • Escherichia coli / physiology
  • Escherichia coli Proteins*
  • Intracellular Membranes / metabolism
  • Membrane Proteins / chemistry
  • Membrane Proteins / immunology
  • Membrane Proteins / metabolism*
  • Membrane Transport Proteins*
  • Molecular Sequence Data
  • Mutagenesis / physiology
  • Protein Precursors / metabolism
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • SEC Translocation Channels
  • SecA Proteins


  • Bacterial Proteins
  • Escherichia coli Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • Protein Precursors
  • SEC Translocation Channels
  • SecG protein, E coli
  • Adenosine Triphosphatases
  • SecA Proteins