Subcellular Sites for Bacterial Protein Export

Mol Microbiol. 2004 Sep;53(6):1583-99. doi: 10.1111/j.1365-2958.2004.04278.x.

Abstract

Most bacterial proteins destined to leave the cytoplasm are exported to extracellular compartments or imported into the cytoplasmic membrane via the highly conserved SecA-YEG pathway. In the present studies, the subcellular distributions of core components of this pathway, SecA and SecY, and of the secretory protein pre-AmyQ, were analysed using green fluorescent protein fusions, immunostaining and/or immunogold labelling techniques. It is shown that SecA, SecY and (pre-)AmyQ are located at specific sites near and/or in the cytoplasmic membrane of Bacillus subtilis. The localization patterns of these proteins suggest that the Sec machinery is organized in spiral-like structures along the cell, with most of the translocases organized in specific clusters along these structures. However, this localization appears to be independent of the helicoidal structures formed by the actin-like cytoskeletal proteins, MreB or Mbl. Interestingly, the specific localization of SecA is dynamic, and depends on active translation. Moreover, reducing the phosphatidylglycerol phospholipids content in the bacterial membrane results in delocalization of SecA, suggesting the involvement of membrane phospholipids in the localization process. These data show for the first time that, in contrast to the recently reported uni-ExPortal site in the coccoïd Streptococcus pyogenes, multiple sites dedicated to protein export are present in the cytoplasmic membrane of rod-shaped B. subtilis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism
  • Anti-Bacterial Agents / pharmacology
  • Bacillus subtilis / drug effects
  • Bacillus subtilis / genetics
  • Bacillus subtilis / physiology*
  • Bacillus subtilis / ultrastructure
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Cell Membrane / chemistry
  • Cell Membrane / metabolism
  • Chloramphenicol / pharmacology
  • Enzyme Inhibitors / pharmacology
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Immunohistochemistry
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism
  • Phospholipids / chemistry
  • Phospholipids / metabolism
  • Protein Transport / physiology*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Rifampin / pharmacology
  • SEC Translocation Channels
  • SecA Proteins

Substances

  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Enzyme Inhibitors
  • Escherichia coli Proteins
  • Membrane Transport Proteins
  • Phospholipids
  • Recombinant Fusion Proteins
  • SEC Translocation Channels
  • SecY protein, E coli
  • Green Fluorescent Proteins
  • Chloramphenicol
  • Adenosine Triphosphatases
  • SecA Proteins
  • Rifampin