Ueki Tatsuya, Shintaku Koki, Yonekawa Yuki, Takatsu Nariaki, Yamada Hiroshi, Hamada Toshiyuki, Hirota Hiroshi, Michibata Hitoshi
Molecular Physiology Laboratory, Department of Biological Science, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan.
Biochim Biophys Acta. 2007 Jun;1770(6):951-7. doi: 10.1016/j.bbagen.2007.02.003. Epub 2007 Feb 17.
Several species of ascidians, the so-called tunicates, accumulate extremely high levels of vanadium ions in their blood cells. We previously identified a family of vanadium-binding proteins, named Vanabins, from blood cells and blood plasma of a vanadium-rich ascidian, Ascidia sydneiensis samea. The 3-dimensional structure of Vanabin2, the predominant vanadium-binding protein in blood cells, has been revealed, and the vanadium-binding properties of Vanabin2 have been studied in detail. Here, we used Far Western blotting to identify a novel protein that interacts with Vanabin2 from a blood cell cDNA library. The protein, named Vanabin-interacting protein 1 (VIP1), was localized in the cytoplasm of signet ring cells and giant cells. Using a two-hybrid method, we revealed that VIP1 interacted with Vanabins 1, 2, 3, and 4 but not with Vanabin P. The N-terminal domain of VIP1 was shown to be important for the interaction. Further, Vanabin1 was found to interact with all of the other Vanabins. These results suggest that VIP1 and Vanabin1 act as metal chaperones or target proteins in vanadocytes.
几种被称为被囊动物的海鞘在其血细胞中积累了极高水平的钒离子。我们之前从富含钒的海鞘——萨氏海鞘（Ascidia sydneiensis samea）的血细胞和血浆中鉴定出了一个钒结合蛋白家族，命名为钒结合蛋白（Vanabins）。血细胞中主要的钒结合蛋白Vanabin2的三维结构已被揭示，并且对Vanabin2的钒结合特性进行了详细研究。在此，我们利用Far Western印迹法从血细胞cDNA文库中鉴定出一种与Vanabin2相互作用的新蛋白。该蛋白名为Vanabin相互作用蛋白1（VIP1），定位于印戒细胞和巨细胞的细胞质中。利用双杂交方法，我们发现VIP1与Vanabins 1、2、3和4相互作用，但不与Vanabin P相互作用。VIP1的N端结构域被证明对这种相互作用很重要。此外，发现Vanabin1与所有其他Vanabins相互作用。这些结果表明，VIP1和Vanabin1在钒细胞中充当金属伴侣或靶蛋白。
