Table 1.
Association rate constants for binding of cyanide to neuroglobin (Ngb)
| T (min) | k obs (M−1 s−1) | |
|---|---|---|
| WTox (A isomer) | 19 | 1.75 |
| WTox (B isomer) | 97 | 0.34 |
| WTred (A isomer) | 127 | 0.26 (K d = 153 μM) |
| WTred (B isomer) | 265 | 0.12 (K d = 316 μM) |
| C120Sox (A isomer) | 18 | 1.85 |
| C120Sox (B isomer) | 119 | 0.28 |
| C120Sred (A isomer) | 138 | 0.24 |
| C120Sred (B isomer) | 255 | 0.13 |
| TM (A isomer) | 262 | 0.12 (K d = 2 mM) |
| TM (B isomer) | 223 | 0.14 (K d = 5 mM) |
The time constants (T) as obtained from the exponential fit to the experimental intensities shown in Fig. 4 are reported for every Ngb state. The second-order rate constants (k obs) were calculated from the time constant and cyanide concentration (500 μM) assuming a linear relationship (1/T = k obs[CN−]). When determined, the dissociation constants (K d) calculated on the basis of the concentrations of the free and bound species at equilibrium are also reported.
WT ox oxidized wild-type Ngb, WT red reduced wild-type Ngb, C120S ox oxidized C120S mutant, C120S red reduced C120S mutant, TM C46G/C55S/C120S triple mutant