Improved synthesis of Salmonella typhimurium enterotoxin using gene fusion expression systems

A. K. Chopra, Allan Brasier, M. Das, Xir Xin-Jing, J. W. Petersoir

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Salmonella enterotoxin (Stn) is a virulence factor in S. typhimurium strain Q1 that causes both fluid secretion in ligated intestinal loops of rabbits and elongation of Chinese hamster ovary (CHO) cells. High-level expression systems are needed to provide Stn in soluble form for detailed study of the biological activity of Stn. To maximize the synthesis and solubility of Stn, we systematically compared the production of native Stn synthesized with a T7 RNA polymerase/promoter system to that of two fusion proteins: glutathione S-transferase::Stn (Gst::Stn) and thioredoxin A::Stn (TrxA::Stn). The latter fusion protein expression systems resulted in a 64-fold increase in Gst::Stn and TrxA::Stn antigen concentration, as measured by specific anti-peptide antibodies in an enzyme-linked immunosorbent assay (ELISA). Most of the toxin derived using these vector systems was insoluble; however, the solubility of the TrxA::Stn antigen increased by at least 50-fold, with a concomitant increase in CHO cell elongation activity. In addition, stn gene expression was enhanced more than 50-fold by addition of 0.2-0.4 M NaCl to Luria-Bertani medium. The biological activity of Stn also was increased in the high-osmolarity medium. Consequently, the expression of stn may be regulated by DNA supercoiling.

Original languageEnglish (US)
Pages (from-to)81-85
Number of pages5
Issue number1
StatePublished - Jun 24 1994


  • DNA sequencing
  • DNA supercoiling
  • PCR
  • Virulence factor
  • anti-peptide antibodies
  • glutathione S-transferase
  • phage T7 RNA polymerase/promoter system
  • thioredoxin

ASJC Scopus subject areas

  • Genetics


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