Table 2.
Gaseous ligand on and off-rates and equilibrium constants at pH 9
| Heme Protein | Gas Ligand Type | k+gasa (mM−1s−1) | k-gasb (s−1) | Kd gas_penc (μM) | Kd,actuald (μM) | k+his (s−1) | k-his (s−1) | KA,hise |
|---|---|---|---|---|---|---|---|---|
| HP7-H7Ff | CO | 220 ± 10 | 0.067 ± 0.002 | 0.30 ± 0.01 | 9 ± 2 | 160 ± 20 | 5.6 ± 0.3 | 29 ± 5 |
| O2 | 1200 ± 200 | 4.8 ± 0.4 | 3.9 ± 0.9 | 120 ± 50 | ||||
| FHFH | CO | 300 ± 90 | 0.071 ± 0.007 | 0.24 ± 0.07 | 2 ± 1 | 210 ± 40 | 24 ± 1 | 9 ± 2 |
| O2 | 1200 ± 300 | 4.1 ± 0.3 | 3 ± 1 | 40 ± 20 |
a
On rate for gaseous ligand binding to the pentacoordinate heme.
b
Rate of gaseous ligand dissociation.
c
Gaseous ligand dissociation constant to the pentacoordinate heme.
d
Gaseous ligand heme dissociation constant.
e
Association constant for distal histidine ligation.
f
Data for HP7-H7F taken from Ref, (4).