Table 3.
Hb | Subunit | k′R (μM−1 s−1) | kR (s−1) | KR (μM−1) | Overall KR (μM−1) | k′T (μM−1 s−1) |
---|---|---|---|---|---|---|
Hb | α | 2.9 | 0.019±0.001 | 152 | 268 | 0.23±0.01 |
β | 9.0 | 474 | ||||
MP4 | α | 4.1 | 0.022±0.001 | 186 | 264 | 0.38±0.04 |
β | 12.0 | 0.032±0.003 | 375 | 4.44±1.57 |
Subunit assignments were based on the fast and slow rates from Table 1, which were assigned to β and α subunits, respectively. ‘R-state' dissociation rates are reported from the NO ligand displacement reactions in Table 1. The equilibrium constants for CO binding to the subunits with ‘R-state' Hbs were calculated from the ratio of the rate constants, KR=k′R kR−1. Overall KR was calculated as KR=(KRα × KRβ)1/2, according to Equation (4).