Table 1.

Apparent K_ds of wild-type and mutant MTF⋅Met-tRNA_N complexes

MTF	Apparent Kd (μM)
	Wild-type tRNA	G72 mutant tRNA
Wild type	.45†	0.5
	.32†	—
R42K	.4
R42L	4.16

Data are based on results of gel mobility shift analyses (29). The binding reactions contained either the wild-type MTF (2.5 μM), the R42K mutant (2.5 μM), or the R42L mutant (5 μM) and increasing amounts of Met-tRNA_N, wild-type, or the G72 mutant (0.25 μM to 1.5 μM). The apparent K_d values were calculated from the slope of a double reciprocal plot of 1/r, where r is the fraction of MTF bound to Met-tRNA_N against 1/Met-tRNA_N free using the equation 1/r = K_d (1/Met-tRNA_N free) + 1 (30, 31). The apparent K_d measured here for the His-tagged wild-type MTF⋅Met-tRNA_N complex using gel mobility shift experiments is about the same as the K_d reported for MTF⋅Met-tRNA complex based on quenching of tryptophan fluorescence of MTF (32). 

^†Results of separate set of experiments.