Structural basis for the high-affinity binding of nucleoporin Nup1p to the Saccharomyces cerevisiae importin-β homologue, Kap95p
Structural basis for the high-affinity binding of nucleoporin Nup1p to the Saccharomyces cerevisiae importin-β homologue, Kap95p
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DOI：
10.1016/j.jmb.2005.04.003
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发表时间：
2005-06-10
影响因子：
5.6
通讯作者：
Stewart, M
中科院分区：
文献类型：
--
作者：
Liu, SM;Stewart, M
大分子最常通过由HEAT重复序列构建的karyopherin/importin-beta超家族成员转运穿过核膜。Kap 95 p（酵母输入蛋白-β），蛋白质输入的主要载体，通过核孔复合物的运输是通过与含有FG重复的核孔蛋白的相互作用来促进的。然而，Nup 1 p与Kap 95 p的相互作用比其他FG-核孔蛋白更强。为了建立这种增加的亲和力的基础，我们确定了与Nup 1 p残基963-1076复合的Kap 95 p的结构，这些残基含有高亲和力Kap 95 p结合位点。Nup 1 p在HEAT重复序列5、6、7和8的外A螺旋之间的三个位点结合Kap 95 p。在每个位点，Nup 1 p的苯丙氨酸残基被埋在相邻HEAT重复序列之间的疏水凹陷中。尽管Nup 1 p和Kap 95 p上的通用FG-核孔蛋白结合位点重叠，但Nup 1 p结合显著不同，并且具有来自额外疏水残基的贡献，以及Nup 1残基977-997与Kap 95 p之间的接头紧密接触产生的相互作用。该接头的长度和组成是至关重要的，并表明FG-核孔蛋白之间和内部对Kap 95 p的亲和力的差异是如何产生的。(c)2005爱思唯尔有限公司保留所有权利。
Macromolecules are transported across the nuclear envelope most frequently by karyopherin/importin-beta superfamily members that are constructed from HEAT repeats. Transport of Kap95p (yeast importin-beta), the principal carrier for protein import, through nuclear pore complexes is facilitated by interactions with nucleoporins containing FG repeats. However, Nup1p interacts more strongly with Kap95p than other FG-nucleoporins. To establish the basis of this increased affinity, we determined the structure of Kap95p complexed with Nup1p residues 963-1076 that contain the high-affinity Kap95p binding site. Nup1p binds Kap95p at three sites between the outer A-helices of HEAT repeats 5, 6, 7 and 8. At each site, phenylalanine residues from Nup1p are buried in hydrophobic depressions between adjacent HEAT repeats. Although the Nup1p and generic FG-nucleoporin binding sites on Kap95p overlap, Nup1p binding differs markedly and has contributions from additional hydrophobic residues, together with interactions generated by the intimate contact of the linker between Nup1 residues 977-997 with Kap95p. The length and composition of this linker is crucial and suggests how differences in affinity for Kap95p both between and within FG-nucleoporins arise. (c) 2005 Elsevier Ltd. All rights reserved.