![]() Studies of L226P showed that hyperpolarization to -147 mV gives half-maximal activation, 123 mV more negative than WT. ![]() Remarkably, three proline-substitution mutations on the same face of S6 as G219 yielded channels that activated upon hyperpolarization and inactivated very slowly. Five of 15 proline-substitution mutants yielded depolarization-activated Na + channels, but only G219P channels have strongly negatively shifted voltage dependence of activation, demonstrating specificity for bending at G219 for depolarization-activated gating. Here we have probed S6 pore-lining residues of NaChBac by proline mutagenesis. Proline residues favor bending of α-helices, and substitution of proline for this glycine (G219) dramatically stabilizes the open state of a bacterial Na + channel NaChBac. Transmembrane helices that line the pore (M2 or S6) are thought to gate it at the cytoplasmic end by bending at a hinge glycine residue. ![]() Members of the voltage-gated-like ion channel superfamily have a conserved pore structure.
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