Na+ channel a-subunit structure II Outside Inside O2H ++++++十 I异亮氨酸;F苯丙氨酸;M甲硫氨酸 RVIRLARIGRILRLIRGAKGIR nactivation“Gate IvS4 Voltage40 CO2H Outside NH2 + + + + + + + + + + + + Inside Na+ Channel a1 -Subunit Structure I II III IV RVIRLARIGRILRLIKGAKGIR + + + + + + + + I F M I F M - Inactivation “Gate” IVS4 Voltage Sensor NH2 CO 2 H b1 I异亮氨酸；F苯丙氨酸；M甲硫氨酸