SecA, an essential component of the secretory machinery of Escherichia coli, exists as homodimer

Biochem Biophys Res Commun. 1991 Jan 15;174(1):211-6. doi: 10.1016/0006-291x(91)90507-4.


Size exclusion chromatography of the cytosolic fraction of SecA-overproducing cells of Escherichia coli suggested that SecA, an essential component of the secretory machinery, exists as an oligomer. The subunit structure of SecA was then studied using a purified specimen. Estimation of the molecular mass by means of ultracentrifugation and chemical crosslinking analysis revealed that SecA exists as a homodimer. The purified SecA was denatured in 6 M guanidine-HCl and renatured to a dimer, which was fully active in terms of translocation, even in the presence of 1 mM dithiothreitol. It is suggested that the dimeric structure is not critically maintained by disulfide bonding between the two subunits, each of which contains four cysteine residues.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / chemistry*
  • Bacterial Proteins / chemistry*
  • Biological Transport
  • Cross-Linking Reagents / chemistry*
  • Cytosol / chemistry
  • Cytosol / drug effects
  • Disulfides
  • Dithiothreitol / pharmacology
  • Escherichia coli / chemistry*
  • Escherichia coli / drug effects
  • Escherichia coli Proteins*
  • Membrane Transport Proteins*
  • Protein Denaturation
  • SEC Translocation Channels
  • SecA Proteins
  • Ultracentrifugation


  • Bacterial Proteins
  • Cross-Linking Reagents
  • Disulfides
  • Escherichia coli Proteins
  • Membrane Transport Proteins
  • SEC Translocation Channels
  • Adenosine Triphosphatases
  • SecA Proteins
  • Dithiothreitol