Taura T, Schlenstedt G, Silver P A
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School and the Dana Farber Cancer Institute, Boston, Massachusetts 02115, USA.
J Biol Chem. 1997 Dec 12;272(50):31877-84. doi: 10.1074/jbc.272.50.31877.
A conserved family of Ran binding proteins (RBPs) has been defined by their ability to bind to the Ran GTPase and the presence of a common region of approximately 100 amino acids (the Ran binding domain). The yeast Saccharomyces cerevisiae genome predicts only three proteins with canonical Ran binding domains. Mutation of one of these, YRB1, results in defects in transport of macromolecules across the nuclear envelope (Schlenstedt, G., Wong, D. H., Koepp, D. M., and Silver, P. A. (1995) EMBO J. 14, 5367-5378). The second one, encoded by YRB2, is a 327-amino acid protein with a Ran binding domain at its C terminus and an internal cluster of FXFG and FG repeats conserved in nucleoporins. Yrb2p is located inside the nucleus, and this localization relies on the N terminus. Results of both genetic and biochemical analyses show interactions of Yrb2p with the Ran nucleotide exchanger Prp20p/Rcc1. Yrb2p binding to Gsp1p (yeast Ran) as well as to a novel 150-kDa GTP-binding protein is also detected. The Ran binding domain of Yrb2p is essential for function and for its association with Prp20p and the GTP-binding proteins. Taken together, we suggest that Yrb2p may play a role in the Ran GTPase cycle distinct from nuclear transport.
一类保守的Ran结合蛋白（RBP）家族已通过其与Ran GTP酶结合的能力以及一个约100个氨基酸的共同区域（Ran结合结构域）的存在得以界定。酵母酿酒酵母基因组预测只有三种具有典型Ran结合结构域的蛋白质。其中之一YRB1发生突变会导致大分子跨核膜运输出现缺陷（施伦施泰特，G.，黄，D. H.，科普，D. M.，以及西尔弗，P. A.（1995年）《欧洲分子生物学组织杂志》14卷，5367 - 5378页）。第二种由YRB2编码，是一种327个氨基酸的蛋白质，在其C端有一个Ran结合结构域，并且在核孔蛋白中保守的FXFG和FG重复序列有一个内部簇。Yrb2p位于细胞核内，这种定位依赖于N端。遗传分析和生化分析结果均显示Yrb2p与Ran核苷酸交换蛋白Prp20p/Rcc1存在相互作用。还检测到Yrb2p与Gsp1p（酵母Ran）以及一种新的150 kDa GTP结合蛋白的结合。Yrb2p的Ran结合结构域对于其功能以及与Prp20p和GTP结合蛋白的关联至关重要。综上所述，我们认为Yrb2p可能在与核运输不同的Ran GTP酶循环中发挥作用。
