Hooking She3p onto She2p for myosin-mediated cytoplasmic mRNA transport.
Hooking She3p onto She2p for myosin-mediated cytoplasmic mRNA transport.
复制标题
将 She3p 连接到 She2p 上以实现肌球蛋白介导的细胞质 mRNA 转运。
DOI：
10.1073/pnas.1423194112
复制
发表时间：
2015
影响因子：
11.1
通讯作者：
Shi,Hang
中科院分区：
文献类型：
--
作者：
Singh,Nimisha;Blobel,Günter;Shi,Hang
大约24种不同的mRNA从酵母母细胞质到子细胞质的分离是真核mRNA转运的经典范例。转运信息存在于长度为40-100 nt的mRNA元件中，称为“邮政编码”。有针对性的运输需要正确定位的肌动蛋白丝和合作装载的mRNA货物肌球蛋白。负载到肌球蛋白的货物使用肌球蛋白4蛋白（Myo 4p）、swi 5 p依赖性HO表达2蛋白（She 2 p）和3蛋白（She 3 p）以及邮政编码。我们先前确定了Myo 4p和She 3 p的晶体结构，它们的1：2化学计量和相互作用组;我们还表明，马达复合物组装需要两个Myo 4p/She 3 p异源三聚体，一个She 2 p四聚体和至少一个单一的zipcode，以在体外产生2：4：4：1化学计量的[Myo 4p/She 3 p/She 2 p/zipcode]稳定复合物。在这里，我们报告了一个结构在2.8- 100分辨率的共晶体的She 2 p四聚体绑定到一个片段的She 3 p。在这种晶体结构中，She 3 p片段形成一个醒目的钩，与四聚体的每个She 2 p亚基表面上的浅疏水口袋结合。She 3 p钩和同源She 2 p结合口袋都由高度保守的残基组成。我们还发现了一个高度保守的区域She 3 p上游的钩区。因为这个区域由碱性和芳香族残基组成，它可能代表了She 3 p对邮政编码的结合活性的一部分。由于She 2 p也表现出zipcode结合活性，我们建议将She 3 p“钩住”She 2 p，使它们的每个zipcode结合活性对齐到一个高亲和力位点，从而将马达组装与zipcode连接起来。
The segregation of approximately two dozen distinct mRNAs from yeast mother to daughter cell cytoplasm is a classical paradigm for eukaryotic mRNA transport. The information for transport resides in an mRNA element 40–100 nt in length, known as “zipcode.” Targeted transport requires properly positioned actin filaments and cooperative loading of mRNA cargo to myosin. Cargo loading to myosin uses myosin 4 protein (Myo4p), swi5p-dependent HO expression 2 protein (She2p) and 3 protein (She3p), and zipcode. We previously determined a crystal structure of Myo4p and She3p, their 1:2 stoichiometry and interactome; we furthermore showed that the motor complex assembly requires two Myo4p⋅She3p heterotrimers, one She2p tetramer, and at least a single zipcode to yield a stable complex of [Myo4p⋅She3p⋅She2p⋅zipcode] in 2:4:4:1 stoichiometry in vitro. Here, we report a structure at 2.8-Å resolution of a cocrystal of a She2p tetramer bound to a segment of She3p. In this crystal structure, the She3p segment forms a striking hook that binds to a shallow hydrophobic pocket on the surface of each She2p subunit of the tetramer. Both She3p hook and cognate She2p binding pocket are composed of highly conserved residues. We also discovered a highly conserved region of She3p upstream of its hook region. Because this region consists of basic and aromatic residues, it likely represents part of She3p’s binding activity for zipcode. Because She2p also exhibits zipcode-binding activity, we suggest that “hooking” She3p onto She2p aligns each of their zipcode-binding activities into a high-affinity site, thereby linking motor assembly to zipcode.