Mode of Action of the FixT Repressor Protein of Sinorhizobium Meliloti

fixT was recently identified as a repressor of nitrogen fixation gene expression in S. meliloti. Here we report on the characterization of the mode of action of FixT. We propose that FixT primarily counteracts the activity of the FixLJ two-component system, by decreasing its phosphorylation state. Specifically, we have found that FixT is an inhibitor of the sensor haemoprotein kinase FixL.