Effects of N-terminal deletions of the Escherichia coli protein Fis on growth rate, tRNA(2Ser) expression and cell morphology.

The Escherichia coli Fis protein is known to be involved in a variety of processes, including the activation of stable RNA operons. In this paper we study the ability of a set of N-terminal Fis deletion mutants to stimulate transcription of the tRNA(2Ser) gene. The results indicate that the domain of the Fis protein containing residues 1-26 is not required for transcription activation. The Fis mutants that are still active in transcription stimulation can also complement the reduced growth rates of Fis- cells, suggesting that the same activating domain is involved in this phenomenon. In addition, we show that in fast growing cultures in the absence of an active Fis protein, minicells are formed. These minicells seem to arise from septum formation near the cell poles. Suppression of minicell formation by Fis also does not require the presence of the N-terminal domain of the protein.