TABLE 1.

Kinetic constants obtained from the fit to the conformational change model of sensorgrams acquired for the binding of different concentrations of tRNA (19.5 nm to 8 μm) to various SerRS mutants

Only for mutant R94A steady state affinity model was used (text).

SerRS variant	ka1	kd1	ka2	kd2	KD	Relative KDa	χ2b
	m−1s−1/105	s−1/10−1	s−1/10−2	s−1/10−3	m/10−7
WT	1.471 ± 0.010	1.239 ± 0.009	1.482 ± 0.006	2.513 ± 0.003	1.22	1	2.71
R38A	0.442 ± 0.001	0.342 ± 0.001	0.832 ± 0.004	9.949 ± 0.017	4.22	3.5	0.20
R78A	0.558 ± 0.002	0.417 ± 0.002	1.204 ± 0.004	4.192 ± 0.006	1.93	1.6	0.28
K79A	0.299 ± 0.001	0.231 ± 0.001	0.283 ± 0.002	7.543 ± 0.029	5.61	4.6	0.18
K87A	0.983 ± 0.013	0.714 ± 0.011	1.345 ± 0.014	3.552 ± 0.011	1.52	1.2	1.95
K88A	1.175 ± 0.004	0.862 ± 0.003	0.993 ± 0.002	2.703 ± 0.002	1.57	1.3	0.53
Y89A	0.568 ± 0.002	0.498 ± 0.003	1.048 ± 0.004	5.494 ± 0.008	3.01	2.5	0.20
K90A	0.572 ± 0.005	0.547 ± 0.006	1.606 ± 0.005	4.568 ± 0.006	2.12	1.7	0.77
R94A					58.10 ± 1.70	47.6	0.07
K141A	0.264 ± 0.001	0.237 ± 0.001	0.515 ± 0.003	6.169 ± 0.013	4.89	4.0	1.34
N142A	1.423 ± 0.005	1.212 ± 0.004	0.673 ± 0.002	5.578 ± 0.005	3.86	3.2	0.77
R143A	0.324 ± 0.001	0.444 ± 0.002	0.605 ± 0.004	11.27 ± 0.03	8.90	7.3	0.09

^aRelative K_D is determined as K_D(mutant)/K_D(WT).

^bStatistical value describing the closeness of fit. Values <10 are acceptable (34).