PMC Biophysics

Table 1 The cation binding affinities for 7E15 variants

From: Inverse tuning of metal binding affinity and protein stability by altering charged coordination residues in designed calcium binding proteins

Protein	Residues					Charge	K _d
	15	56	58	62	64		Tb³⁺ (μM)^a	La³⁺ (μM)^a	Ca²⁺ (mM)^b
CD2	N	E	L	D	K	-1	NB	NB	NB
EEDDD	E	E	D	D	D	-5	0.4 ± 0.2	0.5 ± 0.1	0.10 ± 0.05
EEDDE	E	E	D	D	E	-5	0.8 ± 0.2	0.7 ± 0.1	1.1 ± 0.4
EEDDN	E	E	D	D	N	-4	6.3 ± 0.6	2.2 ± 0.4	2.1 ± 0.5
EEDDQ	E	E	D	D	Q	-4	14 ± 3	3.2 ± 0.7	0.7 ± 0.2
EENDN	E	E	N	D	N	-3	> 30	> 15	> 10
NENDN	N	E	N	D	N	-2	NB	NB	NB

Buffer condition: 20 mM PIPES-10 mM KCl, pH 6.8. NB: No observed binding. a: from Tb³⁺-FRET. b: from NMR HSQC.

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