Energetics and selectivity of the accumulation of vanadium by ascidians

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We found the highest concentration of 350 mM vanadium in the blood cells of Ascidia gemmata belonging to the suborder Phlebobranchia, which concentration corresponds 10^7 times higher than that in sea water.On the other hand, considering the pathway of accululation of vanadium from seawater, it should be appropriate that some proteins participate in the pathway, although the results reported hitherto seem to indicate that vanadium is present in a free, noncomplexed form or associated with low molecular weight components in ascidians. We attempted to extract proteins that bind or associate with vanadium in ascidians. Consequently, using a combined technique of SDS-PAGE and atomic absorption spectrometry, we first succeeded to isolate at least four different types of vanadium-binding proteins, approx. 100kDa, 40kDa, 15kDa, and 12.5kDa and to analyze amico acid sequences of them partially.