Disruption of the gene for Met-tRNA(f)/(Met) formyltransferase severely impairs growth of Escherichia coli

In bacteria, as well as in chloroplasts and mitochondria, the free amino group of the methionylated initiator tRNA(f)/(Met) is specifically modified by the addition of a formyl group. The importance of this modification remains unclear. With the availability of pure Escherichia coli 10- formyltetrahydrofolate:L-methionyl-tRNA(f)/(Met) N-formyltransferase, the enzyme catalyzing Met-tRNA(f)/(Met) formylation, the corresponding fmt gene and its flanking regions were cloned and sequenced. The chromosomal fmt gene was disrupted, and strains modified in their formylation activity were constructed. A depletion of the cellular formylation activity was accompanied by a decrease in the growth rate of the bacteria. At 37°C, in a rich medium, the absence of a functional fmt gene reduced the growth rate of 0.28 doubling per h, from 2.3 for the control strain. At 42°C, the studied fmt mutant strain did not grow further.