Table 1.

Kinetic folding parameters of X11 PDZ1-PDZ2 and PDZ1

pH	kF (s−1)	kU (s−1)	KN–I
X11 PDZ1-PDZ2
3.7	0.14 ± 0.02	0.16 ± 0.02	(2.72 ± 0.08) •10−2
4.5	1.30 ± 0.08	0.078 ± 0.003	(5.7 ± 0.1) •10−4
5.5	5.06 ± 0.05	0.068 ± 0.002	(2.45 ± 0.04) •10−5
6.5	8.32 ± 0.05	0.071 ± 0.001	(8.12 ± 0.02) •10−6
7.0	12.0 ± 0.1	0.077 ± 0.002	(8.19 ± 0.06) •10−6
7.5	11.2 ± 0.1	0.107 ± 0.003	(6.53 ± 0.09) •10−6
9.0	16.3 ± 0.1	0.077 ± 0.001	(8.47 ± 0.04) •10−6
PDZ1
3.7	0.36 ± 0.05	0.32 ± 0.02	-
4.5	1.51 ± 0.04	0.19 ± 0.05	-
5.5	3.7 ± 0.04	0.16 ± 0.06	-
6.5	4.5 ± 0.05	0.16 ± 0.07	-
7.0	5.5 ± 0.03	0.34 ± 0.06	-
7.5	5.8 ± 0.07	0.38 ± 0.08	-
9.0	7.3 ± 0.06	0.33 ± 0.05	-

Folding parameters obtained for X11 PDZ1-PDZ2 and PDZ1 were calculated from a three-state and two-state, respectively. All data were recorded at 37 °C. To reduce errors, the chevron plots of each protein were globally fitted with shared m-values. For X11 PDZ1-PDZ2, the calculated m values from a three-state analysis were m_F = 0.94 ± 0.03 kcal mol⁻¹ M⁻¹; m_U = 0.15 ± 0.02 kcal mol⁻¹ M⁻¹; m_KN–I = 1.09 ± 0.09 kcal mol⁻¹ M⁻¹, with a total m_D–N = 2.2 ± 0.1. This value is in good agreement with the value of 2.1 ± 0.2 kcal mol⁻¹ M⁻¹ obtained from CD monitored denaturation experiments. On the other hand, in the case of PDZ1, a two-state fit returned the values of m_F = 1.04 ± 0.04 kcal mol⁻¹ M⁻¹ and an m_F = 0.15 ± 0.01 kcal mol⁻¹ M⁻¹ with a total m_D–N = 1.2 ± 0.1 kcal mol⁻¹ M⁻¹. Also in this case, there is a good agreement with the equilibrium value monitored by CD melting, being m_D–N = 1.0 ± 0.1 kcal mol⁻¹ M⁻¹.