Trivedi Subrata, Ueki Tatsuya, Yamaguchi Nobuo, Michibata Hitoshi
Marine Biological Laboratory, Graduate School of Science, Hiroshima University, Japan.
Biochim Biophys Acta. 2003 Nov 30;1630(2-3):64-70. doi: 10.1016/j.bbaexp.2003.09.007.
Ascidians, especially those belonging to the suborder Phlebobranchia, can accumulate high levels of vanadium. Vanadium-binding proteins (vanabins) were first isolated from a vanadium-accumulating ascidian, Ascidia sydneiensis samea, and then the vanabins were cloned, their expression was studied, and metal-binding assays were conducted. In order to unravel the mechanism of vanadium accumulation, we searched for vanabin-like genes in other animals, including other ascidians. A database search revealed five groups of cDNAs that encoded vanabin-like proteins in another ascidian, Ciona intestinalis. The genes encoding C. intestinalis vanabins, CiVanabin1 to CiVanabin5, were clustered in an 8.4-kb genomic region. The direction of transcription of each gene was identical and each gene had a single intron. All the C. intestinalis vanabins were cysteine-rich, and the repetitive pattern of cysteines closely resembled that of A. sydneiensis samea vanabins. Using immobilized metal ion affinity chromatography (IMAC), we found that a recombinant protein of at least one of the C. intestinalis vanabins (CiVanabin5) bound to vanadium(IV) ions.
海鞘，尤其是属于静脉鳃亚目的那些海鞘，能够积累高水平的钒。钒结合蛋白（钒蛋白）最初是从一种积累钒的海鞘——萨氏海鞘（Ascidia sydneiensis samea）中分离出来的，随后对钒蛋白进行了克隆、研究其表达情况并开展了金属结合分析。为了阐明钒积累的机制，我们在包括其他海鞘在内的其他动物中寻找类钒蛋白基因。数据库搜索揭示了在另一种海鞘——玻璃海鞘（Ciona intestinalis）中有五组编码类钒蛋白的cDNA。编码玻璃海鞘钒蛋白（CiVanabin1至CiVanabin5）的基因聚集在一个8.4千碱基的基因组区域。每个基因的转录方向相同，且每个基因都有一个内含子。所有玻璃海鞘钒蛋白都富含半胱氨酸，并且半胱氨酸的重复模式与萨氏海鞘钒蛋白的非常相似。使用固定化金属离子亲和色谱法（IMAC），我们发现玻璃海鞘至少一种钒蛋白（CiVanabin5）的重组蛋白与钒（IV）离子结合。
