Table 1. Dissociation constant K_D of substrate-binding proteins.

			KD (µM)
Protein*		Ligand	Freely-diffusing protein	Surface-tethered protein	KD WT protein¶ (µM)
OpuAC(V360C/N423C)	Glycine betaine		3.4 ± 0.4†	3.1‡	4–5 (Wolters et al., 2010)
OppA(A209C/S441C)	RPPGFSFR		7.0 ± 1†	14 ± 5#	5 ± 3#
SBD2(T369C/S451)	Glutamine		1.2 ± 0.2§	0.5‡	0.9 ± 0.1 (Gouridis et al., 2015)
SBD1(T159C/G87C)	Asparagine		0.34 ± 0.03§	0.3‡	0.2 ± 0.0 (Gouridis et al., 2015)
MalE(T36C/S352C)	Maltose		1.7 ± 0.3†	2.2‡	1-2 (Hall et al., 1997a, Kim et al., 2013)
MalE(T36C/S352C)	Maltotriose		0.6 ± 0.2†	0.9‡	0.2-2 (Hall et al., 1997a, Kim et al., 2013)

*. K_D could not be determined reliably for labeled PsaA due to background metal contamination.

†. Population of the closed conformation $P$ in the presence of a ligand concentration $L$ was determined using solution-based smFRET. The $K_D=L(1-P)/P$ for a one-binding site model. Data corresponds to mean ± s.d. of duplicate experiments with the same protein sample.

‡. Figure 2—figure supplement 1.

§. Figure 4—figure supplement 2.

#. Figure 2—figure supplement 2.

¶. The K_D values of wildtype (WT) proteins are obtained from the indicated references.