Expression and characterization of the cloned Salmonella typhimurium enterotoxin

Rajendra Prasad, Ashok Chopra, Parvathi Chary, Johnny Peterson

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Abstract

Earlier, our laboratory reported the cloning of a chromosomally encoded cholera toxin (CT)-like enterotoxin gene from Salmonella typhimurium Q1 into pBR322. Cell lysates from the plasmid clone pC1, containing a 4.8 kb EcoR1 DNA fragment from Salmonella, caused elongation of Chinese hamster ovary (CHO) cells and this biologic activity was neutralized by anti-CT. However, this cloned gene product did not elicit fluid secretion in the rabbit intestinal loop (RIL) model, because of poor expression. We report here, subcloning of a 4.8 kb EcoRI and a 2.7 kb HindIII EcoRI fragment into a high expression T7 RNA polymerase/promoter system. Cell lysates from these clones elicited fluid secretion in the RIL model, caused firm induration in rabbit skin and elongated CHO cells. These biological activities were neutralized by anti-CT. SDS-PAGE and subsequent fluorographic analysis of Escherichia coli, harboring recombinant plasmids in a T7 expression system, revealed the presence of two prominent 35S-labeled polypeptides of 25 and 12 kDa, which were immunoprecipitated with anti-CT. The enterotoxin appeared to be 125 kDa in size, based on chromatography on a P-300 column, had a pl of 6.6 to 6.8, and was heat-labile (60 °C/5 min). Unlike cloned CT and heat-labile enterotoxin (LT-I), which were localized in the periplasm, the Salmonella enterotoxin was cytoplasmic in nature.

Original languageEnglish (US)
Pages (from-to)109-121
Number of pages13
JournalMicrobial Pathogenesis
Volume13
Issue number2
DOIs
StatePublished - 1992

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Keywords

  • Chinese hamster ovary (CHO) cells
  • cholera toxin
  • G-ganglioside ELISA
  • Salmonella enterotoxin (stn)
  • T7 RNA polymerase/promoter

ASJC Scopus subject areas

  • Microbiology
  • Infectious Diseases

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