Vanabins (also known as vanadium-associated proteins or vanadium chromagen) are a class of metalloproteins containing vanadium. Found only in the blood of some ascidians and tunicates (sea squirts), these organisms are able to concentrate vanadium to a level more than 100 times higher than in the surrounding seawater. Vanabin proteins seem to be involved in collecting and accumulating this metal ion. At present there is no conclusive understanding of why these organisms collect vanadium, and it remains a biological mystery. In biochemistry, a metalloprotein is a generic term for a protein that also contains a metal cofactor. ... General Name, Symbol, Number vanadium, V, 23 Chemical series transition metals Group, Period, Block 5 , 4 , d Density, Hardness 6110 kg/m3, 7. ... Red blood cells (erythrocytes) are present in the blood and help carry oxygen to the rest of the cells in the body Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). ... Orders Aplousobranchia Enterogona Phlebobranchia Pleurogona Stolidobranchia Ascidiacea (commonly known as the ascidians) is an order in the Urochordata subphylum of sac-like marine filter feeders. ... Classes Ascidiacea Thaliacea Appendicularia Urochordata (sometimes known as tunicata and commonly called urochordates, tunicates or sea squirts) is the subphylum of saclike filter feeders with input and output siphons. ... Sea water is water from a sea or ocean. ...

Theories

Vanabins as oxygen carriers

Because of the high concentration of vanadium in the blood, it has been assumed that vanabins are used for oxygen transport like iron-based hemoglobin or copper-based hemocyanin. Unfortunately no scientific evidence can be found to back this hypothesis. Respiration is the process of exchanging oxygen and carbon dioxide between an organism and its external environment (breathing). ... 3-dimensional structure of hemoglobin Hemoglobin or haemoglobin is the iron-containing oxygen-transport metalloprotein in the red cells of the blood in mammals and other animals. ... Single Oxygenated Hemocyanin protein from Octopus Hemocyanins (also spelled haemocyanins) are respiratory proteins containing two copper atoms that reversibly bind a single oxygen molecule (O2). ... A hypothesis (= assumption in ancient Greek) is a proposed explanation for a phenomenon. ...

The highest concentration of vanadium found so far, 350 mM, was found in the blood cells of Ascidia gemmata belonging to the suborder Phlebobranchia. This concentration is 107 times higher than that in seawater. The mole (symbol: mol) is one of the seven SI base units and is commonly used in chemistry. ... Scientific classification - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ...

Vanabins accumulate vanadium in the blood cells and reduce V³⁺ and V⁴⁺ from V⁵⁺ with the use of NADPH. Vanabins also transport the reduced vanadium ions into the vacuoles of vanadocytes (vanadium-containing blood cells). The vacuoles are kept at a very acidic pH of 1.9, made possible by pumping hydrogen ions into the vacuoles by use of energy intensive H⁺-ATPase. All the use of NADPH and ATP to collect and maintain the vanadium is extremely energy intensive, unusual for oxygen transporting proteins. The most fundamental reactions in chemistry are the redox processes. ... Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are two important coenzymes found in cells. ... Adenosine triphosphate (ATP) Adenosine triphosphate (ATP) is the nucleotide known in biochemistry as the molecular currency of intracellular energy transfer; that is, ATP is able to store and transport chemical energy within cells. ...

Other oxygen transporting proteins have a very low dissociation constant with their metal prosthetic group and bind these groups tightly. Vanabins on the other hand have a moderate dissociation constant and do not tightly bind vanadium. Most importantly, because of this moderate dissociation constant, vanadium is usually found free-floating and separated from any proteins inside the vacuoles. This is completely different from other oxygen transporting proteins. This article needs cleanup. ... A coenzyme (a. ...

The most convincing evidence against vanadium in use for oxygen transport is that many ascidians and tunicates also have hemocyanin in their blood that could be assumed to handle all oxygen transport. Single Oxygenated Hemocyanin protein from Octopus Hemocyanins (also spelled haemocyanins) are respiratory proteins containing two copper atoms that reversibly bind a single oxygen molecule (O2). ...

Vanabins not oxygen carriers

The use of vanabins and vanadium for oxygen transport in ascidians and tunicates is doubtful. Another hypothesized reason for these organisms collecting vanadium is to make themselves toxic to predators, parasites and microorganisms.

Technological use of vanabins

The world oceans carry diluted concentrations of rare minerals. Total amount of gold, silver, manganese, and platinum (among others) in all the world's oceans rivals that of terrestrial mines, yet because of the diluted nature of these minerals in sea water, cost effective extraction has been considered improbable. Understanding the mechanisms behind how some organisms concentrate rare minerals from sea water could make it biotechnologically possible to grow and farm organisms to filter sea water and extract these minerals.

External links

• http://www.sci.u-szeged.hu/kkk/vanadium4/Michibata.pdf
• Transferring vanabin genes to bacteria (http://aem.asm.org/cgi/content/full/69/11/6442)
• Ascidian News (http://depts.washington.edu/ascidian/AN52.html)
• Gold from the sea (http://www.goldfever.com/gold_sea.htm)