A novel vanadium reductase, Vanabin2, forms a possible cascade involved in electron transfer

Kawakami Norifumi

Ueki Tatsuya

Amata Yusuke

Kanamori Kan

Matsuo Koichi

Gekko Kunihiko

Michibata Hitoshi

Biochimica et Biophysica Acta. Proteins and Proteomics

The unusual ascidian ability to accumulate high levels of vanadium ions at concentrations of up to 350 mM, a 107-fold increase over that found in seawater, has been attracting interdisciplinary attention for a century. Accumulated VV is finally reduced to VIII via VIV in ascidian vanadocytes. Reducing agents must therefore participate in the reduction. Previously, we identified a vanadium-binding protein, Vanabin2, in which all 18 cysteines form nine disulfide bonds. Here, we report that Vanabin2 is a novel vanadium reductase because partial cleavage of its disulfide bonds results in the reduction of VV to VIV. We propose that Vanabin2 forms a possible electron transfer cascade from the electron donor, NADPH, via glutathione reductase, glutathione, and Vanabin2 to the acceptor, and vanadium ions conjugated through thiol-disulfide exchange reactions.

Ascidian

Vanadium

Vanabin2

Redox

Thiol-disulfide exchange reaction

Biology [ 460 ]

eng

Elsevier B.V.

Copyright (c) 2009 Elsevier B.V.

[DOI] 10.1016/j.bbapap.2009.01.007

[PMID] 19336037

[ISSN] 1570-9639

[NCID] AA11685085

[DOI] http://dx.doi.org/10.1016/j.bbapap.2009.01.007 isVersionOf