The crystal structure of annexin Gh1 from Gossypium hirsutum reveals an unusual S3 cluster -: Implications for cellulose synthase complex formation and oxidative stress response
The crystal structure of annexin Gh1 from Gossypium hirsutum reveals an unusual S3 cluster -: Implications for cellulose synthase complex formation and oxidative stress response
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DOI：
10.1046/j.1432-1033.2003.03612.x
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发表时间：
2003-06-01
期刊：
影响因子：
--
通讯作者：
Wlodawer, A
中科院分区：
文献类型：
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作者：
Hofmann, A;Delmer, DP;Wlodawer, A
来自陆地棉（棉纤维）的重组膜联蛋白Gh 1的三维晶体结构已经被确定并在2.1埃的分辨率下被细化到0.219的最终R因子。这种植物膜联蛋白由典型的“膜联蛋白折叠”组成，与以前解决的甜椒膜联蛋白Anx 24（Ca 32）相似，但与非植物膜联蛋白的结构相比，存在显著差异。与哺乳动物膜联蛋白AnxA 5的结构的比较表明，典型的钙结合是几何可能的膜环内的结构域I和II的Anx（Gh 1）在其目前的构象。所有植物膜联蛋白在第一结构域的AB环中具有保守的色氨酸残基;发现该残基在甜椒膜联蛋白Anx 24（Ca 32）中采用环内和环外构象。在Anx（Gh 1）中，保守的色氨酸残基位于表面暴露的位置，位于Anx 24（Ca 32）中观察到的两种构象之间的一半。本结构揭示了一个不寻常的硫簇形成的两个半胱氨酸和甲硫氨酸域II和III，分别。虽然两个半胱氨酸都采用还原的硫醇盐形式并且相隔约5.5埃的距离，但甲硫氨酸残基的硫原子与它们紧邻并且显然与两个半胱氨酸硫原子相互作用。虽然半胱氨酸残基在至少五种植物膜联蛋白和膜联蛋白家族的几种哺乳动物成员中是保守的，但甲硫氨酸残基仅在三种植物蛋白中是保守的。这些膜联蛋白携带的保守残基中的几个已被牵连在氧化应激反应。因此，我们推测，在本结构中发现的半胱氨酸基序，或可能甚至整个硫簇，形成氧化应激反应中膜联蛋白功能的分子基础。
The three-dimensional crystal structure of recombinant annexin Gh1 from Gossypium hirsutum (cotton fibre) has been determined and refined to the final R -factor of 0.219 at the resolution of 2.1 Angstrom. This plant annexin consists of the typical 'annexin fold' and is similar to the previously solved bell pepper annexin Anx24(Ca32), but significant differences are seen when compared to the structure of nonplant annexins. A comparison with the structure of the mammalian annexin AnxA5 indicates that canonical calcium binding is geometrically possible within the membrane loops in domains I and II of Anx(Gh1) in their present conformation. All plant annexins possess a conserved tryptophan residue in the AB loop of the first domain; this residue was found to adopt both a loop-in and a loop-out conformation in the bell pepper annexin Anx24(Ca32). In Anx(Gh1), the conserved tryptophan residue is in a surface-exposed position, half way between both conformations observed in Anx24(Ca32). The present structure reveals an unusual sulfur cluster formed by two cysteines and a methionine in domains II and III, respectively. While both cysteines adopt the reduced thiolate forms and are separated by a distance of about 5.5 Angstrom, the sulfur atom of the methionine residue is in their close vicinity and apparently interacts with both cysteine sulfur atoms. While the cysteine residues are conserved in at least five plant annexins and in several mammalian members of the annexin family of proteins, the methionine residue is conserved only in three plant proteins. Several of these annexins carrying the conserved residues have been implicated in oxidative stress response. We therefore hypothesize that the cysteine motif found in the present structure, or possibly even the entire sulfur cluster, forms the molecular basis for annexin function in oxidative stress response.