Table 1.

Ligand binding parameter values for the ferrous and ferric sGC and Ns H-NOX.

	KD (M)	kOFF, (s−1)	kON, (M−1s−1)	Commentsb
sGC
CO	2.6 × 10−4	10.7	4 × 104	4 °C
NO	4.2 × 10−12 a	6 × 10−4	1.4 × 108	6c (on)/5c (off), 10 °C
O2	N/A	N/A	N/A	No O2 binding at 1 atm, 10 °C
CN−	0.92 × 10−3	7.2 × 10−5	7.8 × 10−2	10 °C
N3−	2.6 × 10−2	N/D	N/D	10 °C
NS H-NOX
CO	1.4 × 10−6	3.6	3 × 106	6c-CO complex
NO	1.7 × 10−10	0.05	3 × 108	1st 6c-NO complex
	0.8 × 10−6	1.9	2.4 × 106	2nd 6c-NO complex
O2	N/A	N/A	N/A	Auto-oxidation
CN−	6.5 × 10−4	N/A	0.03c	[CN−]-dependent saturationd
N3	5.4 × 10−4	N/A	N/A	Limited by Met dissociation

^acalculated as k_OFF/ k_ON using values from ref. (29, 50), N/A - not applicable, N/D - not determined.

^bUnless otherwise specified, the experimental temperature was 20 – 25 °C.

^cThe dissociation constant for the 2^nd step, k₋₂.

^dBiphasic kinetics.