Characterization of a mutationally altered dihydropteroate synthase contributing to sulfathiazole resistance in Escherichia coli

Gayatri Vedantam, Brian P. Nichols

Research output: Contribution to journalArticle

17 Scopus citations


A series of Escherichia coli strains were selected for increasing resistance to sulfathiazole. Resistance occurred in seven increments, suggesting the accumulation of several mutations that contributed to overall sulfathiazole resistance. All of the resistant strains had a sulfathiazole- resistant dihydropteroate synthase with a Pro to Ser substitution at amino acid position 64. Overproduction of the wild-type enzyme did not result in sulfathiazole resistance, however overproduction of the mutant enzyme resulted in significant resistance. Conversely, overproduction of the wild- type enzyme in a sulfathiazole-resistant background resulted in a decrease in resistance. Although the specific activity of DHPS in crude extracts was not significantly different from the wild type, the amino acid substitution resulted in an enzyme with a tenfold increase in the Km for p-aminobenzoate, and a 100-fold increase in the Ki for sulfathiazole.

Original languageEnglish (US)
Pages (from-to)91-97
Number of pages7
JournalMicrobial Drug Resistance
Issue number2
StatePublished - Jan 1 1998


ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Pharmacology
  • Microbiology (medical)

Cite this