State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.
Ecotoxicology. 2012 Aug;21(6):1633-41. doi: 10.1007/s10646-012-0952-x. Epub 2012 Jun 19.
A new metallothionein (MT) gene was cloned from Kandelia candel, a mangrove plant with constitutional tolerance to heavy metals, by rapid amplification of cDNA ends and named KMT, which is composed of two exons and one intron. The full length of KMT cDNA was 728 bp including 121 bp 5' noncoding domain, 240 bp open reading frame and 384 bp 3' termination. The coding region of KMT represented a putative 79 amino acid protein with a molecular weight of 7.75 kDa. At each of the amino- and carboxy-terminal of the putative protein, cysteine residues were arranged in Cys-Cys, Cys-X-Cys and Cys-X-X-Cys, indicating that the putative protein was a novel type 2 MT. Sequence and homology analysis showed the KMT protein sequence shared more than 60 % homology with other plant type 2 MT-like protein genes. At amino acid level, the KMT was shown homology with the MT of Quercus suber (83 %), of Ricinus communis (81 %) and of Arabidopsis thaliana (64 %). Function studies using protease-deficient Escherichia coli strain BL21 Star ™(DE3) confirmed the functional nature of this KMT gene in sequestering both essential (Zn) and non-essential metals (Cd and Hg) and the E. coli BL21 with KMT can live in 1,000 μmol/L Zn, 120 μmol/L Hg, and 2,000 μmol/L Cd. The information could provide more details of the causative molecular and biochemical mechanisms (including heavy metal sequestration) of the KMT in K. candel or a scientific basis for marine heavy-metal environment remediation with K. candel. This study also provides a great significance of protecting mangrove species and mangrove ecosystem.
从具有重金属组成型耐受能力的红树植物海桑中，通过快速扩增 cDNA 末端克隆到一个新的金属硫蛋白（MT）基因，并将其命名为 KMT，它由两个外显子和一个内含子组成。KMT cDNA 的全长为 728bp，包括 121bp 的 5'非编码区、240bp 的开放阅读框和 384bp 的 3'终止子。KMT 的编码区代表一个假定的 79 个氨基酸的蛋白质，分子量为 7.75kDa。在假定蛋白质的氨基和羧基末端，半胱氨酸残基分别排列在 Cys-Cys、Cys-X-Cys 和 Cys-X-X-Cys 中，表明假定蛋白质是一种新型的 2 型 MT。序列和同源性分析表明，KMT 蛋白序列与其他植物 2 型 MT 样蛋白基因的同源性超过 60%。在氨基酸水平上，KMT 与栓皮栎的 MT（83%）、蓖麻的 MT（81%）和拟南芥的 MT（64%）具有同源性。使用缺乏蛋白酶的大肠杆菌菌株 BL21 Star ™（DE3）进行功能研究证实了这种 KMT 基因在螯合必需金属（Zn）和非必需金属（Cd 和 Hg）方面的功能性质，并且带有 KMT 的大肠杆菌 BL21 可以在 1000μmol/L Zn、120μmol/L Hg 和 2000μmol/L Cd 中生存。这些信息可以为 K. candel 中 KMT 的致分子和生化机制（包括重金属螯合）提供更多细节，或者为利用 K. candel 进行海洋重金属环境修复提供科学依据。本研究还为保护红树林物种和红树林生态系统提供了重要意义。
