The crystal structure of mouse Nup35 reveals atypical RNP motifs and novel homodimerization of the RRM domain
The crystal structure of mouse Nup35 reveals atypical RNP motifs and novel homodimerization of the RRM domain
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DOI：
10.1016/j.jmb.2006.07.089
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发表时间：
2006-10-13
影响因子：
5.6
通讯作者：
Yokoyama, Shigeyuki
中科院分区：
文献类型：
--
作者：
Handa, Noriko;Kukimoto-Niino, Mutsuko;Yokoyama, Shigeyuki
核孔复合体介导大分子穿过核被膜（NE）的运输。脊椎动物核孔蛋白Nup35是酿酒酵母Nup53p的直系同源物，被认为与核被膜相互作用，并且是核形态所必需的。预测脊椎动物Nup35和酵母Nup53p之间高度保守的区域包含一个RNA识别基序（RRM）结构域。由于其与其他RRM结构域的序列同源性较低，在其一级结构中尚未鉴定出RNP1和RNP2基序。在本研究中，我们解析了小鼠Nup35的RRM结构域在2.7 Å分辨率下的晶体结构。Nup35的RRM结构域单体采用了如其他已报道的RRM结构域那样的特征性βαββαβ拓扑结构。该结构使我们能够定位非典型的RNP1和RNP2基序。在RNP基序残基中，位于β-折叠表面的那些残基与典型RRM结构域的不同，而埋在疏水核心中的那些则高度保守。根据分析超速离心实验，RRM结构域在晶体中形成同型二聚体。具有非典型RNP基序的RRM结构域的β-折叠表面主要通过疏水相互作用促成同型二聚化：一个Nup35分子的β4链中的Met236的侧链被二聚体中另一个Nup35分子的β1链中的Phe178的芳香族侧链和β3链中的Trp209夹在中间。这种结构揭示了RRM结构域的一种新的同型二聚化模式。（c）2006爱思唯尔有限公司。保留所有权利。
The nuclear pore complex mediates the transport of macromolecules across the nuclear envelope (NE). The vertebrate nuclear pore protein Nup35, the ortholog of Saccharomyces cerevisiae Nup53p, is suggested to interact with the NE membrane and to be required for nuclear morphology. The highly conserved region between vertebrate Nup35 and yeast Nup53p is predicted, to contain an RNA-recognition motif (RRM) domain. Due to its low level of sequence homology with other RRM domains, the RNP1 and RNP2 motifs have not been identified in its primary structure. In the present study, we solved the crystal structure of the RRM domain of mouse Nup35 at 2.7 A resolution. The Nup35 RRM domain monomer adopts the characteristic beta alpha beta beta alpha beta topology, as in other reported RRM domains. The structure allowed us to locate the atypical RNP1 and RNP2 motifs. Among the RNP motif residues, those on the beta-sheet surface are different from those of the canonical RRM domains, while those buried in the hydrophobic core are highly conserved. The RRM domain forms a homodimer in the crystal, in accordance with analytical ultracentrifugation experiments. The beta-sheet surface of the RRM domain, with its atypical RNP motifs, contributes to homodimerization mainly by hydrophobic interactions: the side-chain of Met236 in the beta 4 strand of one Nup35 molecule is sandwiched by the aromatic side-chains of Phel.78 in the beta 1 strand and Trp209 in the 3 strand of the other Nup35 molecule in the dimer. This structure ieveals a new homodimerization mode of the RRM domain. (c) 2006 Elsevier Ltd. All rights reserved.