Abstract's Details

From the Organismal to the Atomic Using X-ray Spectroscopy The Vanadium Reductases: A Completely New Field of Metalloenzymology
Abstract ID	BIO-09
Presenter	Patrick Frank
Presentation Type	Poster
Full Author List	P. Frank (1,2), R. M. K. Carlson (3), E. Carlson (4), B. Hedman (1), K. O. Hodgson (1,2)
Affiliations	(1) Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, CA 94309 (2) Dept. of Chemistry, Stanford University, Stanford, CA 94305-5080 (3) Chevron Petroleum Technology Co., P.O. Box 1627, Richmond, CA 94802 (4) Dept. of Biochemistry and Biophysics, University of California, San Francisco, CA 94143-0984
Category	Bio/Life Sciences
Abstract	Vanadium K-edge x-ray absorption spectroscopy (XAS) was used to track the uptake and fate of VO²⁺ ion in blood cells of Ascidia ceratodes, after exposure to dithiothreitol (DTT) or to DTT plus VO²⁺. With added VO²⁺, average intracellular [VO(aq)]²⁺ increased from 3% to 5%. DTT induced a new intracellular complex with a ligand array similar to [VO(edta)]^2–, amounting to 6% of the total vanadium. At the same time, the ratio of blood cell [V(H₂O)₆]³⁺to [V(SO₄)(H₂O)₅]⁺ changed in a manner indicating a simultaneous increase in endogenous acidity. Based on these and other results, an ascidian vanadate reductase is proposed. The proposal includes the structure of the enzyme active site, the vanadate-vanadyl-vanadic reduction mechanism, the cellular locale, and elements of the regulatory machinery governing the biological reduction of the vanadate and vanadyl ions by ascidians. Together these initiate the entirely new field of vanadium redox enzymology.
Footnotes
Funding Acknowledgement	This work was supported by grant NIH RR-01209 (to KOH). XAS data were measured at SSRL, which is funded by the DOE Office of Basic Energy Science. The SSRL SMB Program is supported by the NIH National Center for Research Resources, Biomedical Technology Program and by the DOE Office of Biological and Environmental Research.