. 2005 Aug;11(8):1225–1237. doi: 10.1261/rna.2760705

TABLE 1.

Apparent kinetic constants k_f and k_s and dissociation constants (K_d) for the corresponding Rnt1p proteins and RNA substrates

Rnt1p/RNA	k_f ; k_s@70 nM (min⁻¹)	F_∞@70nM	k_f; k_s@120 nM (min⁻¹)	F_∞@120nM	K_d (nM)
WT/WT	8.40 ±1.08; 0.109 ±0.011	0.63	7.47 ±1.09; 0.046 ±0.007	0.72	130 ±13
WT/dU5	3.49 ±0.25; 0.071 ±0.006	0.60	4.48 ±0.25; 0.084 ±0.010	0.53	70 ±5
WT/dA18	0.56 ±0.02; 0.036 ±0.002	0.50	0.51 ±0.02; 0.033 ±0.003	0.54	146 ±27
WT/dA20	0.52 ±0.05; 0.081 ±0.008	0.43	0.40 ±0.03; 0.40 ±0.010	0.42	150 ±6
WT/GAAA	N.D.	N.D.	N.D.	N.D.	273 ±19
K371A/WT	0.51 ±0.04; 0.039 ±0.003	0.54	0.79 ±0.07; 0.085 ±0.006	0.60	276 ±23
K371A/dA18	0.020 ±0.001	0.19	0.020 ±0.001	0.33	N.D.
K371A/dA20	0.029 ±0.001	0.25	0.029 ±0.001	0.36	412 ±49
K371A/GAAA	N.D.	N.D.	N.D.	N.D.	525 ±38
S376E/WT	0.46 ±0.02; 0.027 ±0.001	0.49	1.04 ±0.14; 0.09 ±0.01	0.57	172 ±22
S376E/dA18	0.022 ±0.002	0.08	0.022 ±0.001	0.23	199 ±19
S376E/dA20	0.026 ±0.002	0.10	0.026 ±0.001	0.20	N.D.
S376E/GAAA	N.D.	N.D.	N.D.	N.D.	272 ±42
M368A/WT	2.20 ±0.20; 0.028 ±0.003	0.50	5.13 ±0.38; 0.058 ±0.006	0.59	184 ±60
M368E/WT	0.44 ±0.03; 0.026 ±0.004	0.43	2.06 ±0.15; 0.065 ±0.007	0.59	133 ±8
R372A/WT	1.44 ±0.05; 0.060 ±0.005	0.54	4.20 ±0.76; 0.120 ±0.014	0.64	124 ±25

(WT) Wild-type protein or RNA substrate. Apparent kinetic constants are indicated at two concentrations of Rnt1p and are the average of two independent experiments, except for the WT–WT, M368A–WT, M368E–WT, K371A–WT, R372A–WT, and S376E–WT combinations at 120 nM, which are averages from four independent experiments. Most reaction kinetics were fitted to double exponential kinetics: F(t) = F_∞ + A₁ exp(−k_ft) + A₂ exp(−k_st), where F(t) is the fraction reacted at time t, F_∞ is the fraction reacted at the endpoint of the kinetics (120 min), A₁ and A₂ are the amplitudes of the two phases, and k_f and k_s are the apparent rate constants of the fast and the slow phases, respectively. The K371A/dA18, K371A/dA20, S376E/dA18, and S376E/dA20 kinetics were better fitted to single exponential equations; therefore only one constant is indicated. The K_d values are the average of two independent experiments except for the combinations WT–WT (n = 7), WT–dU5 (n = 4), K371A–WT (n = 3), and S376E–WT (n = 4). (N.D.) Not determined. Errors are the standard deviations obtained from independent experiments.