甜瓜钾离子通道MIRK受Na~＋抑制的分子机理

Molecular Mechanism of Melon Potassium Channel MIRK Inhibited by Na^+

甜瓜钾离子通道MIRK受Na+抑制,本研究通过钾离子通道氨基酸序列比对,发现MIRK与其他钾离子通道在3个位点上有较明显差异。采用基因定点突变方法获得3个MIRK突变体,将突变体在非洲爪蟾卵母(Xenopus laevis oocytes)细胞中表达后利用双向电压钳技术研究了Na+对MIRK通道电流的调整作用,以探索MIRK受Na+抑制的可能氨基酸位点。结果显示,MIRK受外界Na+的抑制不是由其单一氨基酸引起,可能涉及MIRK第232～234位丝氨酸、赖氨酸、谷氨酰胺及第241位天冬酰胺等多个氨基酸的共同调节。

Melon potassium channel MIRK,after heterologous expression in Xenopus laevis oocytes was found an inhibition by external Na＋.In order to investigate the effect of external Na＋on MIRK and explore the molecular base of blockage site（s）,we proceeded our research by performing site-directed mutagenesis experiment after amino acid align and obtained three mutants of MIRK,then,used double electrode voltage clamp techniques as a research tool in this study.The results indicated that the depressing effect was not determined by single amino acid but might involve serine,lysine,glutamine combination from 232–234 sites and asparagines at a 241-site.