Table 1. Biophysical parameters of ion... | Rockefeller University Press

Table 1.

Biophysical parameters of ion binding to and translocation through KtrB

ITC				ACMA	SSM
Ion	r (Å)	K_d^choline (mM)	K_d^lithium (mM)	H⁺ flux	K_m (mM)	τ (ms)
Li⁺	0.60	nd	–		nd	nd
Na⁺	0.95	1.8 ± 0.4	nd	+++	35.5 ± 1.9	45.2 ± 3.0
K⁺	1.33	2.9 ± 0.3	0.091 ± 0.012	++	16.4 ± 1.8	15.2 ± 2.9
Rb⁺	1.48	1.9 ± 0.1	2.4 ± 0.2	+	5.9 ± 0.6	8.3 ± 0.5
Cs⁺	1.69	1.6 ± 0.1	1.7 ± 0.3	−	2.1 ± 0.3	9.2 ± 2.3

ITC				ACMA	SSM
Ion	r (Å)	K_d^choline (mM)	K_d^lithium (mM)	H⁺ flux	K_m (mM)	τ (ms)
Li⁺	0.60	nd	–		nd	nd
Na⁺	0.95	1.8 ± 0.4	nd	+++	35.5 ± 1.9	45.2 ± 3.0
K⁺	1.33	2.9 ± 0.3	0.091 ± 0.012	++	16.4 ± 1.8	15.2 ± 2.9
Rb⁺	1.48	1.9 ± 0.1	2.4 ± 0.2	+	5.9 ± 0.6	8.3 ± 0.5
Cs⁺	1.69	1.6 ± 0.1	1.7 ± 0.3	−	2.1 ± 0.3	9.2 ± 2.3

The ionic radii r are shown in Å (Hille, 2001). ITC: K_d values were obtained from a fit to a single binding isotherm (n = 3). ACMA: H⁺ flux is ranked from best (+++) to worst (−) for each ion. SSM: K_m values obtained from the peak currents measured with SSM-based electrophysiology (n = 3 or 4). The decay times of the transient currents are indicated as τ, which were obtained from one-phase exponential decay fits (n = 3). nd, Not detectable. All errors are given as ±SEM.

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