Institute of Botany, Technische Universität Darmstadt, Darmstadt, Germany.
Traffic. 2009 Oct;10(10):1481-7. doi: 10.1111/j.1600-0854.2009.00962.x. Epub 2009 Jul 8.
For a number of ion channels, including the potassium (K(+)) inward rectifying channel from Arabidopsis thaliana (KAT1), diacidic endoplasmic reticulum (ER) export motifs have been identified. These motifs consist of two acidic amino acids (aspartate (D) and/or glutamate (E)) separated by any amino acid. To specify the role of single acidic amino acids for efficiency of ER export, we analysed a sequence of KAT1 that included the originally identified diacidic ER export motif (DxE) plus an additional D just upstream of the diacidic motif. Analysis of single, double and triple mutations of the acidic amino acids of the DxDxE motif revealed a gradual reduction of ER export depending on the number of mutated acidic residues. The amount of reduction in ER export was not related to the position, but only to the number of mutated acidic amino acids. These results show that a triacidic motif is essential for efficient ER export of KAT1. Function of the triacidic motif probably involves cooperative binding to Sec24.
对于许多离子通道，包括来自拟南芥的钾（K(+))内向整流通道（KAT1），已经确定了二酸性内质网（ER）输出基序。这些基序由两个酸性氨基酸（天冬氨酸（D）和/或谷氨酸（E））组成，中间间隔任何氨基酸。为了指定单个酸性氨基酸对 ER 输出效率的作用，我们分析了 KAT1 的一个序列，其中包括最初确定的二酸性 ER 输出基序（DxE）加上二酸性基序上游的另一个 D。对 DxDxE 基序中酸性氨基酸的单、双和三突变的分析表明，根据突变酸性残基的数量，ER 输出逐渐减少。ER 输出减少的量与位置无关，而仅与突变酸性氨基酸的数量有关。这些结果表明，三酸性基序对于 KAT1 的有效 ER 输出是必需的。三酸性基序的功能可能涉及与 Sec24 的协同结合。
