Vanadium-binding proteins (Vanabins) from a vanadium-rich ascidian Ascidia sydneiensis samea

Ueki Tatsuya

Adachi Takahiro

Kawano Sonoko

Aoshima Masato

Yamaguchi Nobuo

Kanamori Kan

Michibata Hitoshi

Biochimica et biophysica acta

Since the beginning of the last century, it has been known that ascidians accumulate high levels of a transition metal, vanadium, in their blood cells, although the mechanism for this curious biological function remains unknown. Recently, we identified three vanadium-binding proteins (vanabins), previously denoted as vanadium-associated proteins (Kanda et al., 1997), from the cytoplasm fraction of vanadium-containing blood cells (vanadocytes) of the vanadium-rich ascidian Ascidia sydneiensis samea. Here, we describe the cloning, expression, and analysis of the metal-binding ability of vanabins. Recombinant proteins of two independent but related vanabins, vanabin1 and vanabin2, bound to 10 and 20 vanadium(IV) ions with dissociation constants of 2.1 × 10-5 M and 2.3 × 10-5 M, respectively. The binding of vanadium(IV) to these vanabins was inhibited by the addition of copper(II) ions, but not by magnesium(II) or molybdate(VI) ions. Vanabins are the first proteins reported to show specific binding to vanadium ions; this should provide a clue to resolving the problem regarding the selective accumulation of vanadium in ascidians.

Ascidian

Vanadium

Metal accumulation

Biology [ 460 ]

eng

Elsevier Science B.V.

Copyright (c) 2003 Elsevier Science B.V.

[ISSN] 0167-4781

[DOI] 10.1016/S0167-4781(03)00036-8

[PMID] 12697328

[DOI] http://dx.doi.org/10.1016/S0167-4781(03)00036-8 isVersionOf