Formylmethionyl-tRNA Dependence of Amino Acid Incorporation in Extracts of Trimethoprim-Treated <i>Escherichia coli</i>

Abstract

The growth of Escherichia coli cells in rich, thymine-containing medium was stopped by the addition of trimethoprim, an inhibitor of dihydrofolate reductase. In an extract of these cells (supernatant from an extract centrifuged at 30,000g) amino acid incorporation at 0.005 M magnesium-ion concentration, directed by f2 bacteriophage RNA depended strictly on added formylmethionyl-transfer RNA or N 5 -formyltetrahydrofolate. Hydroxylamine inhibited the amino acid incorporation directed by f2 bacteriophage RNA, when N 5 -formyltetrahydrofolate had been added, but had no effect when formylmethionyl-transfer RNA had been added.