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The antifolding activity of SecB promotes the export of the E. coli maltose-binding protein

D N Collier1, V A Bankaitis, J B Weiss

  • 1Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill 27514.

Cell
|April 22, 1988
PubMed

Insights

The E. coli secB gene product, SecB, is crucial for protein export. It binds to precursor maltose-binding protein (MBP), preventing premature folding and ensuring efficient transport out of the cell.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Protein Transport

Background:

  • The secB gene in E. coli is essential for the export of proteins across the inner membrane.
  • Maltose-binding protein (MBP) is a well-studied model system for protein export pathways.

Purpose of the Study:

  • To elucidate the mechanism by which the SecB protein facilitates the export of maltose-binding protein (MBP) in E. coli.
  • To investigate the interaction between SecB and precursor MBP and its role in preventing misfolding.

Main Methods:

  • Investigating the interaction between SecB and precursor MBP using genetic and biochemical approaches.
  • Analyzing the effects of SecB availability on MBP export and folding.
  • Utilizing in vitro synthesis and folding assays to assess SecB's antifolding activity.

Main Results:

  • SecB directly interacts with the mature region of precursor MBP.
  • SecB prevents the premature folding of newly synthesized MBP into an export-incompetent conformation.
  • SecB availability is a limiting factor for MBP export, as evidenced by interference from export-defective MBP species.
  • SecB's absence accelerates MBP folding, while its presence retards it.

Conclusions:

  • SecB acts as a chaperone that maintains precursor MBP in an export-competent state by inhibiting its folding.
  • This antifolding activity is critical for efficient SecB-mediated protein export in E. coli.

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