Protein secretion in gram-negative bacteria: assembly of the three components of ABC protein-mediated exporters is ordered and promoted by substrate binding

EMBO J. 1996 Nov 1;15(21):5804-11.


One of the strategies used by Gram-negative bacteria to secrete proteins across the two membranes which delimit the cells, is sec independent and dedicated to proteins lacking an N-terminal signal peptide. It depends on ABC protein-mediated exporters, which consist of three cell envelope proteins, two inner membrane proteins, an ATPase (the ABC protein), a membrane fusion protein (MFP) and an outer membrane polypeptide. Erwinia chrysanthemi metalloproteases B and C and Serratia marcescens hemoprotein HasA are secreted by such homologous pathways and interact with the ABC protein. Using as protein substrates HasA and GST-PrtC, a chimeric protein which has a glutathione S-transferase moiety fused to a large C-terminal domain of protease C, we developed a simple system to identify proteins bound to the substrate based on substrate affinity-chromatography using heme- or glutathione-agarose. We show an ordered association between the protein substrates and the three exporter components: the substrate recognizes the ABC protein which interacts with the MFP which in turn binds the outer membrane component. Substrate binding is required for assembly of the three components.

MeSH terms

  • ATP-Binding Cassette Transporters / chemistry
  • ATP-Binding Cassette Transporters / metabolism*
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins / metabolism*
  • Binding Sites
  • Biological Transport, Active
  • Carrier Proteins*
  • Collagenases / metabolism
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Gram-Negative Bacteria / genetics
  • Gram-Negative Bacteria / metabolism*
  • Macromolecular Substances
  • Membrane Proteins / metabolism
  • Pectobacterium chrysanthemi / genetics
  • Pectobacterium chrysanthemi / metabolism
  • Recombinant Fusion Proteins / metabolism
  • Serratia marcescens / genetics
  • Serratia marcescens / metabolism


  • ATP-Binding Cassette Transporters
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Carrier Proteins
  • HasA protein, Serratia marcescens
  • Macromolecular Substances
  • Membrane Proteins
  • PrtD protein, Erwinia chrysanthemi
  • PrtF protein, bacteria
  • Recombinant Fusion Proteins
  • Collagenases
  • prtC protein, bacteria