. Author manuscript; available in PMC: 2019 Apr 4.

Published in final edited form as: Biochemistry. 2017 May 31;56(23):2928–2937. doi: 10.1021/acs.biochem.6b01092

Table 2.

Distribution of Regulated Actin States at Low Ca²⁺ Concentrations for Several Types of Troponin

	K_B(pyrene)^a	B_pyrene^b	M_ATPase^c	F_acr/F_acr‑wt^d	B_acrylodan^e
WT	0.15	0.87	0.01	1	0.87(column 2)
C84Y TnC	nd	nd^f	0.02	0.85	0.74
D145E TnC	nd	nd^f	0.01	1.03	0.9
A8V TnC	0.2	0.83	0.01	0.78–0.87	0.68–0.76
Δ14 TnT	nd^f	nd^f	0.04	≈0	≈0
A8V TnC and Δ14 TnT	2.1^f,g	0.31^f,g	0.05	≈0	≈0

From ref 64: K_B = 1/(k_calcium/k_EGTA − 1).

B =1 − M − C. C/B = K_B. B = (1 − M)/(1 + K_B).

From ATPase rate measurements normalized to filaments stabilized in the M state (Figures 2 and 4). ATPase measurements were taken at ionic strengths lower than those used for fluorescence measurements.

Fluorescence amplitudes of acrylodan relative to the wild type give the B state relative to the wild type.

B state estimated from column 4 assuming the wild-type value from pyrene–actin studies.

There is no assurance that K_T is small in these systems as required for calculation of K_B from S1 binding kinetics.

K_B calculated using k_calcium as the average from wild-type and A8V TnC cases. Using k_calcium from the A8V TnC and Δ14 TnT pair would decrease all values of K_B.