Table 3.

Effects of mutations and phosphorylation on Ca²⁺-sensitivity of thin filaments containing troponin from HCM cat hearts.

CAT		All Non-HCM	H1	H2	H3	H5	H7	H12	H13	H14	All HCM
EC50, μM ±SEM, n and p-value (Unpaired t-test relative to non-HCM)	Sliding speed	0.092 ± 0.006	0.060 ± 0.010	0.043 ± 0.004	0.083 ± 0.012	0.056 ± 0.003	0.037 ± 0.002	0.054 ± 0.002	0.048 ± 0.015	0.054 ± 0.010	0.057 ± 0.003
		n = 24	n = 2	n = 3	n = 6	n = 19	n = 3	n = 4	n = 2	n = 5	n = 44
			p = 0.136	p = 0.0080	p = 0.49	p < 0.0001	p = 0.0032	p = 0.015	p = 0.047	p = 0.0095	p < 0.0001
	Fraction motile	0.072 ± 0.004	0.040 ± 0.007	0.039 ± 0.004	0.036 ± 0.001	0.050 ± 0.002	0.029 ± 0.001	0.033 ± 0.003	0.028 ± 0.002	0.053 ± 0.008	0.043 ± 0.002
		n = 26	n = 2	n = 3	n = 6	n = 19	n = 4	n = 4	n = 3	n = 5	n = 46
				p = 0.011	p = 0.0002	p < 0.0001	p = 0.0003	p = 0.0008	p = 0.0011	p = 0.061	p < 0.0001
EC50P/unP ± SEM, n and p-value (Single values compared with 1)	Sliding speed	1.833 ± 0.112	1.091 ± 0.118	0.988 ± 0.049	1.068 ± 0.088	1.098 ± 0.033	0.957 ± 0.021	1.010 ± 0.112	0.991	0.997 ± 0.122	1.050 ± 0.023
		n = 8	n = 2	n = 3	n = 3	n = 10	n = 2	n = 2	n = 1	n = 2	n = 25
		p = 0.0001		p = 0.82	p = 0.52	p = 0.015					p = 0.037
	Fraction motile	1.796 ± 0.055	1.006 ± 0.080	0.960 ± 0.054	1.001 ± 0.015	1.113 ± 0.048	1.051 ± 0.048	0.935 ± 0.022	1.048 ± 0.013	0.838 ± 0.0023	1.030 ± 0.026
		n = 9	n = 2	n = 3	n = 3	n = 10	n = 2	n = 2	n = 2	n = 2	n = 26
		p < 0.0001		p = 0.53	p = 0.94	p = 0.044					p = 0.26
100 μM EGCG EC50 P/unP ± SEM, n and p-value (Unpaired t-test relative to untreated)	Sliding speed	2.32				2.197 ± 0.158			3.377	1.403	2.261 ± 0.277
		n = 1				n = 4			n = 1	n = 1	n = 6
		–				p < 0.0001			–	–	p < 0.0001
	Fraction motile	1.54				1.898 ± 0.225			1.927	1.313	1.805 ± 0.173
		n = 1				n = 4			n = 1	n = 1	n = 6
		–				p = 0.00027			–	–	p < 0.0001
TnT exchange EC50 P/unP ± SEM, n and p-value (Unpaired t-test relative to untreated)	Sliding speed					1.696 ± 0.036
						n = 3
						p < 0.0001
	Fraction motile					1.644 ± 0.052
						n = 3
						p = 0.00016

The EC₅₀ of thin filaments from non-HCM and HCM cats is compared and the effect of TnI phosphorylation on EC₅₀ is plotted for a series of different HCM cat samples, using IVMA. The last two rows show how coupling can be restored by exchange of TnT with wild-type (human sequence) TnT or by EGCG. P-values are given using Students's t-test for HCM compared with non-HCM or for the ratio of EC₅₀ in phosphorylated/unphosphorylated troponin compared with 1. Full details of the IVMA experiments are summarized in Supplementary Table S6.