Peter D, Vu T, Edwards R H
Department of Neurology, University of California School of Medicine, Los Angeles, California 90024, USA.
J Biol Chem. 1996 Feb 9;271(6):2979-86. doi: 10.1074/jbc.271.6.2979.
The vesicular monoamine transporters (VMATs) 1 and 2 show close sequence similarity but substantial differences in apparent substrate affinity and drug sensitivity. To identify structural domains that determine these functional characteristics, chimeric transporters were constructed and their properties were analyzed in a heterologous expression system. The results implicate multiple regions in the recognition of serotonin and histamine and the sensitivity to tetrabenazine. Two domains of VMAT2, one extending from transmembrane domain (TMD) 5 to the beginning of TMD8 and the other from the end of TMD9 through TMD12, increase the affinity for serotonin and histamine as well as the sensitivity to tetrabenazine but only in the context of more C-terminal and more N-terminal VMAT2 sequences, respectively. In addition, the extreme N terminus of VMAT2 alone suffices to confer a partial increase in substrate affinity and tetrabenazine sensitivity. Despite these similarities among the interactions with serotonin, histamine, and tetrabenazine, the region of VMAT2 from TMD3 through TMD4 increases serotonin affinity but not histamine affinity or tetrabenazine sensitivity, and whereas the region from TMD5 to TMD8 of VMAT2 increases serotonin affinity in the context of more C-terminal VMAT2 sequences, the region encompassing TMD5 through TMD7 reduces serotonin but not histamine affinity or tetrabenazine sensitivity in the context of more N-terminal VMAT2 sequences. Thus, the chimeric analysis also reveals differences between serotonin recognition and the recognition of both histamine and tetrabenazine that may account for the observed differences in their interaction with the transport protein.
囊泡单胺转运体（VMATs）1和2在序列上显示出密切的相似性，但在表观底物亲和力和药物敏感性方面存在显著差异。为了确定决定这些功能特征的结构域，构建了嵌合转运体，并在异源表达系统中分析了它们的特性。结果表明，5-羟色胺和组胺的识别以及对丁苯那嗪的敏感性涉及多个区域。VMAT2的两个结构域，一个从跨膜结构域（TMD）5延伸至TMD8起始处，另一个从TMD9末端延伸至TMD12，分别增加了对5-羟色胺和组胺的亲和力以及对丁苯那嗪的敏感性，但仅分别在更C端和更N端的VMAT2序列背景下才如此。此外，单独的VMAT2极端N末端足以使底物亲和力和丁苯那嗪敏感性部分增加。尽管与5-羟色胺、组胺和丁苯那嗪的相互作用存在这些相似性，但VMAT2从TMD3到TMD4的区域增加了5-羟色胺亲和力，但未增加组胺亲和力或丁苯那嗪敏感性；而VMAT2从TMD5到TMD8的区域在更C端的VMAT2序列背景下增加了5-羟色胺亲和力，在更N端的VMAT2序列背景下，包含TMD5至TMD7的区域降低了5-羟色胺亲和力，但未降低组胺亲和力或丁苯那嗪敏感性。因此，嵌合分析还揭示了5-羟色胺识别与组胺和丁苯那嗪识别之间的差异，这可能解释了它们与转运蛋白相互作用中观察到的差异。
