Role of glutamate residues in substrate recognition by human MATE1 polyspecific H+/organic cation exporter
Role of glutamate residues in substrate recognition by human MATE1 polyspecific H+/organic cation exporter
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DOI：
10.1152/ajpcell.00504.2007
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发表时间：
2008-04-01
影响因子：
5.5
通讯作者：
Moriyama, Yoshinori
中科院分区：
文献类型：
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作者：
Matsumoto, Takuya;Kanamoto, Takuji;Moriyama, Yoshinori
人多药毒性化合物外排蛋白1（Human multidrug and toxic compound extrusion 1，hMATE 1）是一种电中性H+/有机阳离子交换剂，负责肾脏和肝脏中结构无关的毒性有机阳离子的最终排泄步骤。为了阐明hMATE 1底物识别的分子基础，我们替换了跨膜区保守的谷氨酸残基Glu 273、Glu 278、Glu 300和Glu 389，并在人胚肾293中表达后，使用四乙基铵（TEA）和西咪替丁作为底物检查所得突变蛋白的转运活性（HEK- 293）细胞。除Glu 273 Ala外，所有这些突变体均在HEK- 293细胞的质膜上完全表达。在突变体Glu 278 Ala中完全不存在TEA转运活性。Glu 300 Ala和Glu 389 Ala以及所有天冬氨酸突变体均表现出显著降低的活性。Glu 273 Asp对西咪替丁表现出更高的亲和力，而对TEA具有降低的亲和力。Glu 278 Asp对西咪替丁的亲和力降低。Glu 300 Asp和Glu 389 Asp对TEA的亲和力均降低，而Glu 389 Asp对西咪替丁的亲和力比野生型转运蛋白高4倍，V-max值降低约4倍。Glu 273 Asp和Glu 300 Asp都改变了TEA吸收的pH依赖性。这些结果表明，所有这些谷氨酸残基参与结合和/或运输的TEA和西咪替丁，但他们的个人角色是不同的。
Human multidrug and toxic compound extrusion 1 ( hMATE1) is an electroneutral H+/organic cation exchanger responsible for the final excretion step of structurally unrelated toxic organic cations in kidney and liver. To elucidate the molecular basis of the substrate recognition by hMATE1, we substituted the glutamate residues Glu273, Glu278, Glu300, and Glu389, which are conserved in the transmembrane regions, for alanine or aspartate and examined the transport activities of the resulting mutant proteins using tetraethylammonium ( TEA) and cimetidine as substrates after expression in human embryonic kidney 293 ( HEK- 293) cells. All of these mutants except Glu273Ala were fully expressed and present in the plasma membrane of the HEK- 293 cells. TEA transport activity in the mutant Glu278Ala was completely absent. Both Glu300Ala and Glu389Ala and all aspartate mutants exhibited significantly decreased activity. Glu273Asp showed higher affinity for cimetidine, whereas it has reduced affinity to TEA. Glu278Asp showed decreased affinity to cimetidine. Both Glu300Asp and Glu389Asp had lowered affinity to TEA, whereas the affinity of Glu389Asp to cimetidine was fourfold higher than that of the wildtype transporter with about a fourfold decrease in V-max value. Both Glu273Asp and Glu300Asp had altered pH dependence for TEA uptake. These results suggest that all of these glutamate residues are involved in binding and/ or transport of TEA and cimetidine but that their individual roles are different.