Characterization of oligomeric human half-ABC transporter ATP-binding cassette G2
Characterization of oligomeric human half-ABC transporter ATP-binding cassette G2
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DOI：
10.1074/jbc.m310785200
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发表时间：
2004-05-07
影响因子：
4.8
通讯作者：
Zhang, JT
中科院分区：
文献类型：
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作者：
Xu, JK;Liu, Y;Zhang, JT
人三磷酸腺苷结合盒G2(ABCG2)是三磷酸腺苷结合盒(ABC)转运蛋白超家族中的一员，具有多种底物。人ABCG2在模型癌细胞中的过表达通过主动分泌抗癌药物而导致多药耐药。与大多数其他ABC转运蛋白不同的是，ABCG2通常有两个核苷酸结合域和两个跨膜域，而ABCG2只由一个核苷酸结合域和一个跨膜域组成。因此，ABCG2被认为是一种半转运体，可能具有同源二聚体的功能。在这项研究中，我们使用非变性洗涤剂全氟辛酸和Triton X-100结合凝胶过滤、蔗糖密度梯度沉淀和凝胶电泳来表征人ABCG2的寡聚特性。出乎意料的是，我们发现人ABCG2主要以四聚体形式存在，可能存在更高形式的寡聚。单体和二聚体ABCG2似乎不是该蛋白的主要形式。进一步的免疫沉淀分析表明，该寡聚体ABCG2不含任何其他蛋白。综上所述，我们得出结论，人类ABCG2可能存在并作为同源四聚体发挥作用。
Human ATP-binding cassette G2 (ABCG2, also known as mitoxantrone resistance protein, breast cancer-resistance protein, ABC placenta) is a member of the superfamily of ATP-binding cassette ( ABC) transporters that have a wide variety of substrates. Overexpression of human ABCG2 in model cancer cell lines causes multidrug resistance by actively effluxing anticancer drugs. Unlike most of the other ABC transporters which usually have two nucleotide-binding domains and two transmembrane domains, ABCG2 consists of only one nucleotide-binding domain followed by one transmembrane domain. Thus, ABCG2 has been thought to be a half-transporter that may function as a homodimer. In this study, we characterized the oligomeric feature of human ABCG2 using non-denaturing detergent perfluorooctanoic acid and Triton X-100 in combination with gel filtration, sucrose density gradient sedimentation, and gel electrophoresis. Unexpectedly, we found that human ABCG2 exists mainly as a tetramer, with a possibility of a higher form of oligomerization. Monomeric and dimeric ABCG2 did not appear to be the major form of the protein. Further immunoprecipitation analysis showed that the oligomeric ABCG2 did not contain any other proteins. Taken together, we conclude that human ABCG2 likely exists and functions as a homotetramer.