Variation and Evolution of Metal Utilization

细胞内低水平的金属离子对氧传递、电子传递、酶活性调节或信号转导等生物功能具有重要作用。各种生物的进化与金属利用的多样性之间的关系日益受到人们的关注。在这项研究中，我们重点研究了钒结合蛋白(Vanabins)，它们被认为是海鞘中钒积累的关键因素。我们打算研究该蛋白是否在富钒虫囊中是独有的，该蛋白是否存在于富钒虫中，如果存在同源蛋白，其功能是什么。最终目标是开创金属利用多样性和演化的新研究领域1。我们用基因组Southern杂交的方法在日本周边海域采集的海鞘中鉴定了与钒类化合物同源的基因，但没有成功。我们通过固定化金属离子亲和层析鉴定了几种与钒相关的蛋白。我们在海鞘的基因组和EST数据库中发现了五个与Vanabins同源的基因。它们聚集在一个很小的基因组区域。我们通过重组蛋白揭示了它们与钒离子结合的能力。我们在另一种海鞘动物Ciona savignyi的基因组数据库中发现了六个与钒离子同源的基因。它们没有分布在基因组的三个相距较远的区域

Metal ions at a low level in cells are important for biological functions such as oxygen transport, electron transfer, regulation of enzyme activity, or signal transduction. There is increasing interest on the relationship between evolution of various organisms and the variety of metal utilization. In this study, we focused on vanadium-binding proteins (vanabins) that are thought to be a key factor for vanadium accumulation in an ascidian, Ascidia sydneiensis samea. We intended to examine whether this protein is unique in vanadium-accumulating ascidian, whether this protein exist in vanadium-accumulating worm, what is the function of homologous proteins if exist. The final goal is to create a new research filed of variety and evolution of metal utilization1. We examined by genomic Southern blot hybridization to identify genes homologous to vanabins in ascidians collected in the sea surrounding Japan, but it failed2. We identified several vanadium-associated proteins by immobilized metal ion affinity chromatography in Pseudopotamilla occelata3. We found five genes homologues to vanabins in genome and EST databases of an ascidian, Ciona intestinalis. They are clustered in a small "genomic region. We revealed their ability to bind vanadium ions by using recombinant proteins4. We found six genes homologous to vanabins in the genome database of another ascidian, Ciona savignyi. They are not distributed in three distant regions in the genome