IDENTIFICATION OF A PROTEIN COMPLEX THAT IS REQUIRED FOR NUCLEAR-PROTEIN IMPORT AND MEDIATES DOCKING OF IMPORT SUBSTRATE TO DISTINCT NUCLEOPORINS
IDENTIFICATION OF A PROTEIN COMPLEX THAT IS REQUIRED FOR NUCLEAR-PROTEIN IMPORT AND MEDIATES DOCKING OF IMPORT SUBSTRATE TO DISTINCT NUCLEOPORINS
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DOI：
10.1073/pnas.92.5.1769
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发表时间：
1995-02-28
影响因子：
11.1
通讯作者：
MOORE, MS
中科院分区：
文献类型：
--
作者：
RADU, A;BLOBEL, G;MOORE, MS
我们已经确定并表征了一个9 S蛋白复合物从非洲爪蟾卵巢胞质亚组分（馏分A），构成这一馏分的活动，在识别模型核进口基板和对接它在核孔复合物。由于其功能，该复合物被称为核转运蛋白。复合物的54-和56-kDa亚基分别被称为α 1和α 2，97-kDa亚基被称为β，在另一种方法中，我们已经确定了从大鼠肝胞质亚组分A的核转运蛋白β通过使用固定化大鼠核孔蛋白Nup 98在一个单一的，基于亲和力的富集步骤。本研究对大鼠核浆细胞转运蛋白β进行了分子克隆和序列测定，与蛋白质数据库的比较表明，该蛋白与其它已知蛋白没有明显的相似性。使用硝化纤维素固定的大鼠肝脏核被膜蛋白和核进口底物作为配体，我们发现非洲爪蟾馏分A依赖结合至少三个真正的核孔蛋白（Nup 214，Nup 153，和Nup 98）和一个候选人的核孔蛋白，估计分子量为270 kDa。我们建议，这些核孔蛋白的功能作为对接蛋白质的核转运蛋白介导的结合底物在核进口/出口途径的核孔复合物。
We have identified and characterized a 9S protein complex from a Xenopus ovary cytosolic subfraction (fraction A) that constitutes this fraction's activity in recognizing a model nuclear import substrate and docking it at the nuclear pore complex. Because of its function, the complex is termed karyopherin. The 54- and 56-kDa subunits of the complex are termed alpha 1 and alpha 2, respectively, and the 97-kDa subunit is termed beta, In an alternative approach we have identified karyopherin beta from a rat liver cytosolic subfraction A by using immobilized rat nucleoporin Nup98 in a single, affinity-based enrichment step. We have molecularly cloned and sequenced rat karyopherin beta, Comparison with protein sequence data banks showed no significant similarity to other known proteins. Using nitrocellulose-immobilized rat liver nuclear envelope proteins and nuclear import substrate as a ligand, we found Xenopus fraction A-dependent binding to at least three bona fide nucleoporins (Nup214, Nup153, and Nup98) and to a candidate nucleoporin with an estimated molecular mass of 270 kDa. We propose that these nucleoporins function as docking proteins for karyopherin-mediated binding of substrate in a nuclear import/export pathway across the nuclear pore complex.