TABLE 1.

ITC thermodynamic parameters of NCS-1 WT, 135H, and 135A

Results of fitting ITC data to a two-site binding model are shown. The program ORIGIN was used to obtain the thermodynamic parameters for NCS-1 WT and both mutants.

ITC Ca2+titration of NCS-1 WT, I35H, and I35A
NCS-1	Site	KA	Kda	ΔHb	ΔSc
		m−1	nm	kcal/mol	kcal/mol
WT	1	6.6 × 107 ± 2.5 × 107	57	−2.37 ± 0.13	7.72
	2	4.7 × 106 ± 2.2 × 106		−3.19 ± 0.50	19.67
I35H	1	7.2 × 107 ± 2.0 × 107	91 nM	−8.28 ± 0.34	7.70
	2	1.7 × 106 ± 3.4 × 105		−4.03 ± 0.58	14.75
I35A	1	1.1 × 106 ± 1.8 × 105	169 nM	−5.50 ± 0.84	8.87
	Site 2	3.2 × 107 ± 6.4 × 106		−1.07 ± 0.25	2.44

^a ΔH, enthalpy.

^b ΔS, entropy of binding.

^c Overall K_d = 1/√K₁K₂.