2005 年 59 巻 5 号 p. 326-331
Rare metals such as vanadium and cobalt are dissolved in seawater at very low concentrations. Ascidians are known to accumulate extremely high levels of vanadium selectively. Vanadium is accumulated mainly in one type of their blood cells, and the concentration reaches 350 mM corresponding to107times that in seawater. Recently, we isolated vanadium-binding proteins, Vanabinl-5, from an vanadium-rich ascidian, Ascidia sydneiensis samea. Biochemical and structural analyses revealed that Vanabins make a novel protein family which is characterized by 18 conserved cysteine motif. They are thought to act as metal chaperones in ascidian blood cells. Vanabins can be used as an agent for selective bioaccumulation and biosorption of heavy metals.