Background：

Potassium channels represent the most complex class of voltage-gated ino channels from both functional and structural standpoints. Their diverse functions include regulating neurotransmitter release， heart rate， insulin secretion， neuronal excitability， epithelial electrolyte transport， smooth muscle contraction， and cell volume. Four sequence-related potassium channel genes - shaker， shaw， shab， and shal - have been identified in Drosophila， and each has been shown to have human homolog(s). This gene encodes a member of the potassium channel， voltage-gated， shaker-related subfamily.?