Two precursors of the heat-stable enterotoxin of Escherichia coli: evidence of extracellular processing

Mol Microbiol. 1990 Feb;4(2):265-73. doi: 10.1111/j.1365-2958.1990.tb00593.x.


Expression of the gene of the methanol-soluble, heat-stable enterotoxin of Escherichia coli (STA) allowed the identification by SDS-PAGE of a cell-associated 7500 Dalton STA-related peptide; when similar experiments were performed with a phosphate buffer SDS-PAGE system, an additional Mr 9800 band became apparent. The 9800 Dalton form, pre-pro-STA, accumulated as an intracellular species when the experiments were performed in the presence of the proton ionophore CCCP (carbonylcyanide m-chlorophenylhydrazone); by pulse-chase experiments, it was shown that pre-pro-STA became a periplasmic Mr 7500 pro-STA and this form was chased to the culture supernatant; periplasmic and extracellular pro-STA showed the same electrophoretic mobility. A short time after the pulse, pro-STA was converted extracellularly to mature STA (Mr 4500). It is proposed that STA is synthesized as pre-pro-STA, a 72-amino-acid peptide that is subsequently cleaved between amino acids 19 and 20 as it is translocated across the inner membrane. The resulting 53-amino-acid pro-STA is first detected in the periplasm and is then secreted to the culture supernatant. Pro-STA is cleaved extracellularly to yield mature STA (Mr 4500).

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Toxins / metabolism*
  • Cysteine / metabolism
  • Enterotoxins / metabolism*
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins
  • Protein Precursors / metabolism*
  • Protein Processing, Post-Translational
  • Recombinant Fusion Proteins / metabolism
  • Sulfur Radioisotopes


  • Bacterial Toxins
  • Enterotoxins
  • Escherichia coli Proteins
  • Protein Precursors
  • Recombinant Fusion Proteins
  • Sulfur Radioisotopes
  • heat stable toxin (E coli)
  • Cysteine