Substitution of Thr for Ala-237 in TEM-17, TEM-12 and TEM-26: alterations in beta-lactam resistance conferred on Escherichia coli

FEMS Microbiol Lett. 2001 Jul 10;201(1):37-40. doi: 10.1111/j.1574-6968.2001.tb10729.x.


Non-naturally occurring mutants of TEM-17 (E104K), TEM-12 (R164S) and TEM-26 (E104K:R164S) extended-spectrum (ES) beta-lactamases bearing threonine at position 237 were constructed by site-specific mutagenesis and expressed under isogenic conditions in Escherichia coli. Quantification of beta-lactamase activities and immunoblotting indicated that Ala-237-->Thr did not significantly affect expression levels of these ES enzymes. Minimum inhibitory concentrations of beta-lactam antibiotics showed that the presence of threonine at position 237 exerted a dominant effect increasing the enzymes' preference for various early generation cephalosporins over penicillins. Activity against broad-spectrum oxyimino-beta-lactams was also changed. The effect of Ala-237-->Thr on the activity against ceftazidime, aztreonam, cefepime and cefpirome of all three ES TEM enzymes was detrimental. Introduction of Thr-237 improved activity against cefotaxime and ceftriaxone in TEM-12 and TEM-26, but not in TEM-17.

MeSH terms

  • Alanine / chemistry
  • Amino Acid Substitution*
  • Anti-Bacterial Agents / metabolism
  • Anti-Bacterial Agents / pharmacology*
  • Escherichia coli / drug effects*
  • Escherichia coli / enzymology
  • Escherichia coli / genetics
  • Isoelectric Point
  • Microbial Sensitivity Tests
  • Mutagenesis, Site-Directed
  • Threonine / chemistry
  • beta-Lactam Resistance / genetics*
  • beta-Lactamases / chemistry
  • beta-Lactamases / genetics*
  • beta-Lactamases / metabolism
  • beta-Lactams


  • Anti-Bacterial Agents
  • beta-Lactams
  • Threonine
  • beta-lactamase TEM-12
  • beta-lactamase TEM-26
  • beta-Lactamases
  • Alanine