TABLE 2.
Summary of kinetic parameters
Shown are the parameters obtained from analyzing presteady-state currents on G457Q and G457E. The table includes values for WT-mSGLT3b from Ref. 12. These data were derived from fits of the Boltzmann equation to Q/V distributions as shown in Fig. 8. Qmax is the total charge movement by the protein. V0.5 is the voltage at which the charge is equally distributed between inward and outward facing conformations, and turnover is the rate at which the protein cycles. All parameters, except V0.5, were similar between both mutants and similar to WT-mSGLT3b. V0.5 in G457E is more depolarized than in G457Q. Data are shown as mean ± S.E. (n = 6–8).
| WT-mSGLT3b | G457E | G457Q | |
|---|---|---|---|
| Imax (nA) | 1800 ± 250 | 1200 ± 130 | 1600 ± 330 |
| Qmax (nC) | 25 ± 4 | 17 ± 2 | 25 ± 4 |
| V0.5 (mV) | −17 ± 1 | 36 ± 2 | 3.3 ± 4 |
| Turnover (cycles sec−1) | 75 ± 3.4 | 76 ± 8 | 64 ± 6 |