Table S1.

Summary of biHis sites in NuG2b

Location	Site	Mutation	ψ0*	ϕbiHis	ΔΔGeqMetal	ΔΔGeqbiHis	ΔΔGfMetal	m0	m0Metal	βT†	βTMetal	Metal
	WT	−	−	−	−	−	−	1.29(7)	−	0.78(5)	−	−
β1 + β2	a	V7H/T16H	1.45(15)	0.67(7)	0.90(11)	−1.91(18)	0.83(5)	1.52(3)	1.38(5)	0.72(2)	0.81(4)	Ni2+
	b	V9H/T14H	1.65(23)	0.89(9)	0.81(6)	−1.21(13)	1.01(3)	1.48(2)	1.32(4)	0.78(2)	0.71(4)	Zn2+
α	c	K29H/Q33H	0.26(3)	0.47(6)	0.92(6)	−1.42(19)	0.40(4)	1.27(4)§	1.29(4)	0.73(3)	0.73(3)	Zn2+
β3 + β4	d	T45H/T54H	0.36(5)	0.38(6)	0.97(6)	−1.13(14)	0.55(3)	1.37(4)§	1.30(5)	0.72(3)	0.71(3)	Zn2+
	e	D47H/T52H	0.80(2)	0.39(2)	−1.08(6)	−2.84(13)	−0.65(5)	1.46(4)¶	1.41(5)	0.85(1)	0.88(1)	Zn2+
β1 + β4	f	K5H/T52H	−0.14(3)	0.32(2)	0.70(4)	−2.55(13)	−0.22(3)	1.33(3)	1.35(2)	0.74(2)	0.72(2)	Zn2+
	g	V7H/T54H	0.02(0)	0.31(3)	2.27(5)	−2.22(15)	0.35(3)	1.37(3)§	1.51(3)	0.70(2)	0.73(3)	Zn2+
	h	V9H/T56H	0.28(2)	0.55(12)	1.27(3)	−0.78(17)	0.67(2)	1.52(3)§	1.45(3)	0.68(1)	0.66(1)	Zn2+
α	i	A25H/K29H	0.19(9)	0.63(17)	1.84(24)	−0.85(28)	0.98(7)	1.29(12)§	1.25(13)	0.61(7)	0.59(7)	Ni2+
	j	Q33H/D37H	0.15(2)	0.30(7)	2.00(8)	−0.83(15)	1.00(4)	1.45(5)§	1.50(5)	074(3)	0.75(3)	Ni2+
β1 + β4	k	V9H/T54H	0.79(15)	ND	0.85(12)	−0.06(9)	0.75(6)	1.23(3)§,‡	1.23(3)	0.81(0)	0.81(0)	Zn2+
	l	V7H/T56H	0.84(6)	0.57(6)	−0.60(7)	−1.72(19)	−0.46(4)	1.47(3)	1.57(6)	0.73(2)	0.79(2)	Ni2+
β2 + α	m	Y17H/Y34H	0.22(3)	0.74(12)	1.60(7)	−1.65(25)	0.85(4)	1.35(4)§	1.25(4)	0.73(3)	0.71(3)	Zn2+

Values in parentheses represent SEs of the fitting and derived parameters, e.g., 1.45(15) = 1.45 ± 0.15. ND, not determined.

^*ψ₀ value is calculated directly in the fit of the chevron data that includes data for strongly folding and unfolding condition, x_f and x_u, respectively (Fig. S4).

^†β_T = m_f/m₀, where m_f and m₀ are the denaturant dependences of the ΔG_f and ΔG_eq, respectively (Materials and Methods).

^§m_u is a shared parameter.

^¶m_f is a shared parameter.

^‡m_u is set to the value obtained from fitting the chevron in the absence of metal ions.