Molecular characterization of an enterotoxin from Salmonella typhimurium

Ashok Chopra, Johnny Peterson, Parvathi Chary, Rajendra Prasad

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

In this study, we describe the molecular and antigenic characteristics of a cloned enterotoxin from Salmonella typhimurium strain Q1. The full length Salmonella enterotoxin gene (stn), localized on a 2.8 kb Cla I/PstI DNA fragment, was cloned from a genomic library of Salmonella . Based on nucleotide sequence analysis, the stn gene contained 749 bp that would encode a protein having a molecular size of 29 073. The most unusual feature of the stn gene was the presence of a rare initiation codon (TTG) in lieu of the typical ATG codon, which required site-directed mutagenesis to confirm the precise initiation site. The expression of the stn gene in a bacteriophage T7 RNA polymerase/promoter system was enhanced by introducing a typical ATG start codon and an optimal Shine-Dalgarno sequence upstream of the stn gene by site-directed mutagenesis. The stn gene was located opposite the hydHG operon that regulates labile hydrogenase activity in Salmonella species and Escherichia coli . The overall amino acid sequence of the enterotoxin was quite dissimilar to any other published sequence, including cholera toxin or other adenylate cyclase-activating proteins. However, an intriguing similarity in a small region of the amino acid sequence of Stn was observed with portions of the amino acid sequences from several other protein toxins known to ADP-ribosylate host cell proteins. This region of homology may indicate a conserved motif, within the active site, that is involved in the stimulation of adenylate cyclase activity.

Original languageEnglish (US)
Pages (from-to)85-98
Number of pages14
JournalMicrobial Pathogenesis
Volume16
Issue number2
DOIs
StatePublished - Feb 1994

Fingerprint

Enterotoxins
Salmonella typhimurium
Amino Acid Sequence
Initiator Codon
Genes
Site-Directed Mutagenesis
Adenylyl Cyclases
Salmonella
Proteins
Hydrogenase
Genomic Library
Cholera Toxin
Operon
Codon
Adenosine Diphosphate
Sequence Analysis
Catalytic Domain
Escherichia coli
Gene Expression
DNA

Keywords

  • anti-peptide antibodies
  • DNA sequencing
  • site-directed mutagenesis
  • Stn
  • stn gene
  • T7 RNA polymerase/promoter system

ASJC Scopus subject areas

  • Infectious Diseases
  • Microbiology

Cite this

Molecular characterization of an enterotoxin from Salmonella typhimurium. / Chopra, Ashok; Peterson, Johnny; Chary, Parvathi; Prasad, Rajendra.

In: Microbial Pathogenesis, Vol. 16, No. 2, 02.1994, p. 85-98.

Research output: Contribution to journalArticle

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