The influence of a local anesthetic on the structure and function of an ion channel was examined, using the membrane-spanning domain of the erythrocyte anion transport protein, band 3, as the model system. The effect of lidocaine on the channel's structure was monitored in situ by highly sensitive differential scanning calorimetry. The influence of lidocaine on the channel's transport function was assayed by following the rate of H35SO4 - exchange across the erythrocyte membrane. The results demonstrate that concentrations of lidocaine which inhibit ion transport also destabilize channel structure. While the uncharged form of lidocaine was a potent perturbant of both ion transport and channel stability, the cationic form of the anesthetic was ineffective in both respects. Based on empirical equations relating the calorimetric and transport properties of the anion channel to lidocaine concentration, the following structure-function relationship was derived: κ κ0 = 1 1 + 0.06(ΔTc)1.6' where ΔTc is the change in the channel's denaturation temperature observed upon addition of sufficient lidocaine to lower the rate constant of anion transport from κ0 (control) to κ. With this expression, the rate of transport in the presence of lidocaine can be predicted from an analysis of the stability of the channel in situ.
ASJC Scopus subject areas
- Molecular Biology