AMINO-TERMINUS AND THE FIRST 4 MEMBRANE-SPANNING SEGMENTS OF THE ARABIDOPSIS K+ CHANNEL KAT1 CONFER INWARD-RECTIFICATION PROPERTY OF PLANT-ANIMAL CHIMERIC CHANNELS
AMINO-TERMINUS AND THE FIRST 4 MEMBRANE-SPANNING SEGMENTS OF THE ARABIDOPSIS K+ CHANNEL KAT1 CONFER INWARD-RECTIFICATION PROPERTY OF PLANT-ANIMAL CHIMERIC CHANNELS
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DOI：
10.1074/jbc.270.30.17697
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发表时间：
1995-07-28
影响因子：
4.8
通讯作者：
SCHROEDER, JI
中科院分区：
文献类型：
--
作者：
CAO, YW;CRAWFORD, NM;SCHROEDER, JI
拟南芥超极化激活（内向整流）的K+通道KAT 1在结构上更类似于动物去极化激活（外向整流）的K+通道比动物超极化激活的K+通道。为了深入了解植物内向整流和动物外向整流K+通道的相反电压依赖性的结构基础，我们构建了超极化激活的K+通道KAT 1和非洲爪蟾去极化激活的K+通道之间的重组嵌合通道。我们在这里报告，两个嵌合体的构建体，其中包含前三分之一的KAT 1序列，包括前四个跨膜段（S1-S4）和第四和第五跨膜段之间的接头序列，表达功能通道，保留激活超极化，但不去极化。这两个嵌合通道对K+不再具有选择性。嵌合体对阳离子的选择性超过阴离子，并且对Ca 2+是可渗透的。因此，与动物超极化激活的K+通道不同，其中羧基末端对于由Mg 2+和多胺阻断诱导的内向整流是重要的，植物KAT 1通道在氨基末端区域具有其内向整流的主要决定因素，该区域终止于S4-S5接头的末端。
The Arabidopsis hyperpolarization-activated (inward-rectifying) K+ channel KAT1 is structurally more similar to animal depolarization-activated (outward-rectifying) K+ channels than to animal hyperpolarization-activated K+ channels. To gain insight into the structural basis for the opposite voltage dependences of plant inward-rectifying and animal outward-rectifying K+ channels, we constructed recombinant chimeric channels between the hyperpolarization-activated K+ channel KAT1 and a Xenopus depolarization-activated K+ channel. We report here that two of the chimeric constructs, which contain the first third of the KAT1 sequence, including the first four membrane-spanning segments (S1-S4) and the linker sequence between the fourth and fifth membrane-spanning segments, express functional channels that retain activation by hyperpolarization, but not depolarization. These two chimeric channels are no longer selective for K+. The chimeras are selective for cations over anions and are permeable to Ca2+. Therefore, unlike animal hyperpolarization-activated K+ channels, in which the carboxyl terminus is important for inward rectification induced by Mg2+ and polyamine block, the plant KAT1 channel has its major determinants for inward rectification in the amino-terminal region, which ends at the end of the S4-S5 linker.