镁(magnesium)是生物生长发育必需的核心营养元素之一,也是细胞中含量最多的两价阳离子.镁具有最大的水合半径,最小的离子半径和最大的电荷密度,特殊的理化性质使其在生物体内的转运方式显得尤为重要.以前的研究大多集中在物化结构,生理功能,缺镁病理等方面,并在光合作用,酶的活化,基因组稳定,抑制衰老,减轻铝害和调节氮代谢等研究方面取得了一定的成就,但Mg2+转运蛋白的晶体结构,Mg2+吸收、转运和体内平衡的分子机理,Mg2+胁迫信号的传导机制等信息仍知之甚少.人们已经从许多生物中克隆了Mg2+转运相关基因,包括原核生物、低等真核生物、高等真核生物,并对其结构、功能、亚细胞定位进行了分析验证.根据已知镁离子运输体的不同结构或功能,把它们分为6个不同的家族:钴抗性蛋白家族(CorA),Mg2+/H+交换体(AtMHX),离子通道,P型磷酸酶(P-type phosphatase),Mg2+转运体基因家族MgtE(MgtE)和其它镁离子运输家族.同一家族的不同成员之间存在结构或功能的相似性,其中,CorA家族的镁离子运输体是最基本、研究最深入的运输体,它们广泛的存在于细菌,酵母菌,动物和植物中,能调节镁离子的吸收和外排.本文对已发现的各种Mg2+转运体的结构功能特点进行了综述,以期为该领域的研究提供一些有益的参考.%Magnesium is the most abundant divalent cation in cells and acts as a critical role in organism growth and development. It has the largest hydrated radius, the smallest ionic radius, and the highest charge density. It is very important for organism to transport magnesium within or among cells because of its specially chemical and physical characteristics. Previous research focused on structural features, physiological function and pathology of magnesium deficiency, and have made great progress in photosynthesis, activating enzymes, stabilizing genomic, inhibiting aging, alleviating Al toxicity and adjusting N metabolism. Our understanding of magnesium crystal structure, signaling of magnesium stress and cellular homeostasis is still in its infancy. Some magnesium transporters have been cloned from organism, such as prokaryote, yeast, mammal and plant, also analyzed the structure, function and subcelluar localization of this magnesium transporters. According to the different structure or function of this magnesium transports, they are divided into six disparate family: Cobalt resistance A (Cor A), Arabidopsis thaliana magnesium-proton exchanger (AtMHX), cation channal, P-type ATPase, magnesium transport E (MgtE) family and other magnesium transports. The structure or function of different members which belong to the same family appears to be closely related. The CorA family is the most extensively studied magnesium transport system, and appears to be the primary magnesium transport system, which exists widely in fungi, bacteria, animals and plants with effectively mediating both influx and efflux of magnesium. This paper reviews the research progress of those magnesium transporter systems, and aims to provide some useful references for the later research.
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