O2-specific regulation of the ferrous heme-based sensor kinase FixL from Sinorhizobium meliloti and its aberrant inactivation in the ferric form.

FixL, a rhizobial heme-based O2-sensing histidine kinase, catalyzes autophosphorylation in the deoxy form at low O2 tension, while the kinase activity is inhibited in the case of the O2-bound form. The present study unambiguously shows that the binding of CO and NO does not significantly inhibit the kinase activity of dithiothreitol (DTT)-reduced ferrous… (More)