Amino Acid Residues in the Putative Transmembrane Domain 11 of Human Organic Anion Transporting Polypeptide 1B1 Dictate Transporter Substrate Binding, Stability, and Trafficking
Amino Acid Residues in the Putative Transmembrane Domain 11 of Human Organic Anion Transporting Polypeptide 1B1 Dictate Transporter Substrate Binding, Stability, and Trafficking
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人有机阴离子转运多肽 1B1 推定跨膜结构域 11 中的氨基酸残基决定转运蛋白底物结合、稳定性和运输
DOI：
10.1021/acs.molpharmaceut.5b00466
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发表时间：
2015-12-01
影响因子：
4.9
通讯作者：
Hong, Mei
中科院分区：
文献类型：
--
作者：
Hong, Weifang;Wu, Zhixuan;Hong, Mei
有机阴离子转运多肽（oats，基因符号SLCO）是一种膜蛋白，介导多种内源性和外源性化合物的钠依赖性转运。由于其广泛的底物特异性、广泛的组织分布和参与药物相互作用，oops被认为是药物吸收、分布和排泄的关键参与者。跨膜结构域（trans - membrane domains, TMs）是许多转运蛋白发挥正常功能的关键结构特征。根据计算机建模和我们实验室等人之前的研究，OATP1B1的TM11可能面对底物相互作用口袋，从而在蛋白质的转运功能中发挥重要作用。跨膜结构域的丙氨酸扫描鉴定了该区域内的七个关键氨基酸残基。进一步分析表明，丙氨酸取代这些残基导致蛋白质稳定性降低，从而导致膜上蛋白质表达显著降低。此外，所有突变体都表现出ES摄取（高亲和力或低亲和力成分，或两者兼而有之）K-m的改变，尽管牛磺胆酸运输的K-m仅在R580A、G584A和F591A中发生了变化。这些结果表明，TM11中的关键残基不仅影响转运蛋白的稳定性，还影响其与底物的相互作用。在21个TM氨基酸中鉴定出7个必需残基，突出了该跨膜结构域在OATP1B1正常功能中的重要性。
Organic anion transporting polypeptides (OATPs, gene symbol SLCO) are membrane proteins that mediate the sodium-independent transport of a wide range of endogenous and exogenous compounds. Due to their broad substrate specificity, wide tissue distribution, and involvement in drug drug interactions, OATPs have been considered as key players in drug absorption, distribution, and excretion. Transmembrane domains (TMs) are crucial structural features involved in proper functions of many transporters. According to computer-based modeling and previous studies of our laboratory and others, TM11 of OATP1B1 may face the substrate interaction pocket and thus play an important role in the transport function of the protein. Alanine-scanning of the transmembrane domain identified seven critical amino acid residues within the region. Further analysis revealed that alanine substitution of these residues resulted in reduced protein stability, which led to significantly decreased protein expression on membrane. In addition, all mutants exhibited an altered K-m for ES uptake (either high affinity or low affinity component, or both), though K-m for taurocholate transport only changed in R580A, G584A, and F591A. These results suggested that critical residues in TM11 not only affect protein stability of the transporter, but its interaction with substrates as well. The identification of seven essential residues out of 21 TM amino acids highlighted the importance of this transmembrane domain in the proper function of OATP1B1.