Factor for inversion stimulation-dependent growth rate regulation of individual tRNA species in Escherichia coli

We have studied the involvement of the factor for inversion stimulation (FIS) in the growth rate-dependent expression of the arginine, leucine, and methionine acceptor tRNA species. The concentration of individual tRNA species relative to 16 S rRNA was determined by blot hybridization using RNA preparations from bacteria with the fis gene deleted and from isogenic wild type bacteria. The RNA preparations were obtained from bacteria growing under steady state conditions in different media. The levels of tRNA(1Leu), tRNA(2Arg), tRNA(4Arg), and tRNA(5Arg decreased in the fis bacteria, relative to the wild type. The difference in levels increased with increasing growth rate. Surprisingly, tRNA(3Leu), tRNA(rMet), and tRNA(eMet) showed the opposite response, with an increase of the tRNA/16 S ratio in the fis bacteria. The tRNA(2Leu, tRNA(4Leu), tRNA(5Leu), and tRNA(3 Arg) had unaffected tRNA/16 S ratios in fis cells. We conclude that FIS, directly or indirectly, is involved in growth rate regulation of some tRNA species and that it affects the composition of the cellular tRNA pool.