vanabins

thumb|3-D representation of the structure of Vanabin2 from Ascisia sydneiensis var. samea

Vanabins (also known as vanadium-associated proteins or vanadium chromagen) are a group of vanadium-binding metalloproteins. Vanabins are found almost exclusively in the blood cells, or vanadocytes, of some tunicates (sea squirts), including the Ascidiacea. The vanabins extracted from tunicate vanadocytes are often called hemovanadins. These organisms are able to concentrate vanadium from the surrounding seawater, and vanabin proteins have been involved in collecting and accumulating this metal ion. At present there is no conclusive understanding of why these organisms collect vanadium.