Table 1. Effect of adenine nucleotides on the oxygen-binding affinity of FixL.

	Kd, μM
FixL	–FixJ	+FixJ
None	50 ± 10	56 ± 8
+ATP	47 ± 6	176 ± 7
+AMP-PCP	nt	55 ± 1
+AMP-PNP	nt	46 ± 9
+ADP	118 ± 30	218 ± 27

K_d values of FixL were determined from the OECs at 25°C. The concentrations of FixL and FixJ in the kinase buffer were 5 and 10 μM, respectively. MnCl₂ and adenine nucleotides were added at the final concentrations of 0.2 mM. nt, not tested.