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A novel vanadium reductase, Vanabin2, forms a possible cascade involved in electron transfer
Norifumi Kawakami1, Tatsuya Ueki, Yusuke Amata
1Department of Biological Science, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan.
Biochimica Et Biophysica Acta
|April 2, 2009
Summary
Ascidians accumulate high vanadium levels. A protein called Vanabin2 acts as a vanadium reductase, reducing vanadium(V) to vanadium(IV) through disulfide bond cleavage, revealing a novel biological mechanism.
Area of Science:
- Biochemistry
- Marine Biology
- Biotechnology
Background:
- Ascidians exhibit a remarkable capacity for accumulating vanadium ions, reaching concentrations up to 350 mM, which is a 10(7)-fold increase compared to seawater.
- The biological significance and mechanism of this extreme vanadium accumulation and intracellular reduction (V(V) to V(III) via V(IV)) remain areas of active research.
Purpose of the Study:
- To investigate the role of the previously identified vanadium-binding protein, Vanabin2, in the vanadium reduction process within ascidians.
- To elucidate the molecular mechanism by which Vanabin2 facilitates vanadium reduction.
Main Methods:
- Analysis of Vanabin2's protein structure, focusing on its nine disulfide bonds.
- Experimental manipulation of Vanabin2's disulfide bonds to observe its effect on vanadium ion reduction.
- Proposed electron transfer cascade involving NADPH, glutathione reductase, glutathione, and Vanabin2.
Main Results:
- Vanabin2 was identified as a novel vanadium reductase.
- Partial cleavage of Vanabin2's disulfide bonds directly resulted in the reduction of vanadium(V) to vanadium(IV).
Conclusions:
- Vanabin2 utilizes the cleavage of its internal disulfide bonds as a mechanism for vanadium reduction.
- A proposed electron transfer pathway involving Vanabin2, initiated by NADPH and mediated by glutathione, facilitates vanadium ion reduction through thiol-disulfide exchange reactions.
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