Role of activating region 1 of Escherichia coli FNR protein in transcription activation at class II promoters

FNR is an Escherichia coil transcription factor that activates gene express ion in response to anaerobiosis at a large number of promoters by making di rect contacts with RNA polymerase, At class II FNR-dependent promoters, whe re the DNA site for FNR overlaps the -35 element, activating region 1 of FN R is proposed to interact with the C-terminal domain of the RNA polymerase alpha-subunit. Using a model class II FNR-dependent promoter, FF(-41.5), we have performed in vivo and in vitro experiments to investigate the role of this interaction. Our results show that FNR, carrying substitutions in act ivating region 1, is compromised in its ability to promote open complex for mation and thus to activate transcription. Abortive initiation assays were used to assess the contribution of activating region 1 of FNR to open compl ex formation. A new method for the purification of the FNR protein is also described.