Table 1.

Association rate constant (k _a), dissociation rate constant (k _d), and dissociation equilibrium constant (K _d) for the interaction of IF2 and the 30S IC

30S IC	IF2	Nucleotide	k a (μM–1 s–1)a	k d (s–1)a	K d (nM)a
30S ICwT	wtIF2	GTP	2.0 ± 0.13b	0.041 ± 0.01b	21 ± 6
30S ICmT	mutIF2	GTP	2.2 ± 0.4b	0.013 ± 0.001b	6.4 ± 1.3
30S ICwD	wtIF2	GDP	2.1 ± 0.12	1.32 ± 0.09	622 ± 28
30S ICmD	mutIF2	GDP	1.2 ± 0.10	0.13 ± 0.01	102 ± 9
30S ICwT,Met	wtIF2	GTP	0.52 ± 0.02c	1.2 ± 0.2	2328 ± 294
30S ICmT,Met	mutIF2	GTP	0.77 ± 0.05	0.11 ± 0.01	136 ± 7
30S ICwT,OH	wtIF2	GTP	0.38 ± 0.02c	2.2 ± 0.5	5842 ± 1469
30S ICmT,OH	mutIF2	GTP	0.74 ± 0.02	0.14 ± 0.02	185 ± 18

^a k _a, k _d, and K _d were obtained from three independently collected data sets (mean ± SE) using a transition probability matrix-based population decay analysis as described previously²⁸ and in Methods section

^b k _a and k _d were corrected for the effects of Cy5 photobleaching

^c k _a was corrected for the effects of Cy3 photobleaching