Metal binding by citrus dehydrin with histidine-rich domains
Metal binding by citrus dehydrin with histidine-rich domains
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DOI：
10.1093/jxb/eri262
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发表时间：
2005-10-01
影响因子：
6.9
通讯作者：
Kuboi, T
中科院分区：
文献类型：
--
作者：
Hara, M;Fujinaga, M;Kuboi, T
脱水蛋白是植物中响应渗透胁迫（例如干旱、寒冷和盐）的亲水性蛋白质。虽然它们被假设为稳定应激细胞中的大分子，但它们的功能尚未完全了解。柑橘苷主要在低温胁迫下积累，通过降低膜脂过氧化作用增强转基因烟草的耐冷性。已经证明柑橘黄酮清除羟基自由基。在这项研究中，金属结合的柑橘黄酮的报告和特定的结构域负责确定。采用固定化金属离子亲和色谱法（IMAC）研究了柑桔苷与金属离子的结合特性。Fe ~（3+）、Co ~（2+）、Ni ~（2+）、Cu ~（2+）和Zn ~（2+）与柑橘黄酮结合，Mg ~（2+）、Ca ~（2+）和Mn ~（2+）与柑橘黄酮不结合。在结合的金属中，检测到最高的亲和力为Cu 2 +-Cu 2+结合，其显示解离常数为1.6 μ M。柑橘黄酮能够结合多达16个Cu 2+离子。IMAC表明，His残基有助于Cu ~（2+）-Cu_2In结合。CuCOR 15的氨基酸序列分为五个结构域，其中结构域1与Cu 2+的结合最强。结构域1的一部分HKGEHHSGDHH是结合的核心序列。这些结果表明，柑橘黄酮使用含有His的特定序列结合金属。由于柑橘黄酮是一种自由基清除蛋白质，它可以降低植物细胞在水分胁迫条件下的金属毒性。
Dehydrins are hydrophilic proteins that are responsive to osmotic stress, such as drought, cold, and salinity in plants. Although they have been hypothesized to stabilize macromolecules in stressed cells, their functions are not fully understood. Citrus dehydrin, which accumulates mainly in response to cold stress, enhances cold tolerance in transgenic tobacco by reducing lipid peroxidation. It has been demonstrated that citrus dehydrin scavenges hydroxyl radicals. In this study, the metal binding of citrus dehydrin is reported and the specific domain responsible is identified. The metal binding property of citrus dehydrin was tested using immobilized metal ion affinity chromatography (IMAC). Fe3+, Co2+, Ni2+, Cu2+, and Zn2+ bound to citrus dehydrin, but Mg2+, Ca2+, and Mn2+ did not. Among the bound metals, the highest affinity was detected for Cu2+-dehydrin binding, which showed a dissociation constant of 1.6 mu M. Citrus dehydrin was able to bind up to 16 Cu2+ ions. IMAC indicated that His residues contributed to Cu2+-dehydrin binding. The amino acid sequence of CuCOR15 was divided into five domains, of which domain 1 bound Cu2+ most strongly. One portion of domain 1, HKGEHHSGDHH, was the core sequence for the binding. These results suggest that citrus dehydrin binds metals using a specific sequence containing His. Since citrus dehydrin is a radical-scavenging protein, it may reduce metal toxicity in plant cells under water-stressed conditions.