Table 1.
Rates and equilibrium constants for hexacoordination by the distal histidine.
| Kinetic and equilibrium constants for reversible distal histidine coordination | |||||
|---|---|---|---|---|---|
| Protein | Emid (mv) | kH2 (s−1) | k–H2 (s−1) | K H2 | Reference |
| Mb | 50 | ~0 | ~0 | [53] | |
| Mb H64V/V68H | −128 | >20,000 | >200 | ~100 | [53]a |
| Ngbhuman | −115 | 1900 | 1.5 | 2000 | |
| Ngbmouse | −129 | 1000 | 0.5 | 2000 | |
| Ngbzebrafish | 2500 | 2 | 1250 | [39], [46,48]b | |
| Cgb | −28 | 315 | 1.3 | ~400 | [40,47] |
| DrosHb | 550 | 30 | 18 | [49] | |
| Mollusk nHb | 14,000 | 1000 | 14 | [41] | |
| Plant nsHb1 (average) | 130 | 75 | 1.7 | ||
| Rice nsHb1 | −143 | 75 | 40 | 1.9 | |
| Plant nsHb2 (average) | 1500 | 25 | 84 | ||
| Tomato nsHb2 | 1400 | 30 | 60 | ||
| SynHb | −195 | 4200 | 14 | 300 | [48] |
a
Average values for members of each class are in bold. The value of KH2 for Mb H64V/V68H is unpublished, and is from a personal communication from John S. Olson; other values are from [53].
b
For Ngb, KH is average of values from these references.