Uptake of vanadium by the ascidian Ascidia ceratodes

Anderson, D.; Berg, John W.; Swinehart, James H.

doi:10.1016/0300-9629(91)90250-g

Cited by 9 publications

(4 citation statements)

References 17 publications

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“…It is now known that whole blood cells of A. ceratodes can directly take up added vanadyl ion in addition to added vanadate [32][33][34], in vitro. The incubation experiments reported here were composed to test whether A. ceratodes blood cells, like those from P. nigra, would produce a new chelated form of V(III) when exposed to DTT.…”

Section: Discussionmentioning

confidence: 99%

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The uptake and fate of vanadyl ion in ascidian blood cells and a detailed hypothesis for the mechanism and location of biological vanadium reduction. A visible and X-ray absorption spectroscopic study

Frank

Carlson²,

Carlson³

et al. 2008

Journal of Inorganic Biochemistry

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Vanadium K-edge x-ray absorption spectroscopy (XAS) has been used to track the uptake and fate of VO 2+ ion in blood cells from Ascidia ceratodes, following exposure to dithiothreitol (DTT) or to DTT plus VO 2+ . The full range of endogenous vanadium was queried by fitting the XAS of blood cells with the XAS spectra of model vanadium complexes. In cells exposed only to DTT, ~0.4% of a new V(III) species was found in a site similar to Na[V(edta)(H 2 O)]. With exposure to DTT and VO 2+ , average intracellular [VO(aq)] 2+ increased from 3% to 5%, and 6% of a new complexed form of vanadyl ion appeared evidencing a ligand array similar to [VO(edta)] 2− . At the same time, the relative ratio of blood cell [V(H 2 O) 6 ] 3+ increased at the expense of [V(H 2 O) 5 (SO 4 )] + in a manner consistent with a significant increase in endogenous acidity. In new UV/visible experiments, VO 2+ could be reduced to 7-coordinate [V(nta)(H 2 O) 3 ] or [V(nta)(ida)] 2− with cysteine methyl ester in pH 6.5 solution. Ascorbate reduced [VO(edta)] 2− to 7-coordinate [V(edta)(H 2 O)] − , while [VO (trdta)] 2− was unreactive. These results corroborate the finding that the reductive EMF of VO 2+ is increased by the availability of a 7-coordinate V(III) product. Finally a new and complete hypothesis is proposed for an ascidian vanadate reductase. The structure of the enzyme active site, the vanadatevanadyl-vanadic reduction mechanism, the cellular locale, and elements of the regulatory machinery governing the biological reduction of vanadate and vanadyl ion by ascidians are all predicted. Together these constitute the new field of vanadium redox enzymology.Phlebobranch ascidians (tunicates) are vanadium-concentrating, filter-feeding marine Urochordates that have a continuous evolutionary history reaching back into the upper Cambrian [1][2][3][4]. Although vanadium in ascidian blood cells has been under active investigation for almost 100 years [5][6][7], the mechanisms of uptake, transport, and reduction of oceanic © 2008 Elsevier Inc. All rights reserved.Contact Information: Dr. Patrick Frank, Tel: 1-650-723-2479, Fax: 1-650-723-4817, frank@ssrl.slac.stanford.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript vanadate remain largely unknown. The biologically unique highly acidic intracellular vacuolar aqua vanadium (III, IV) solutions, concentrated primarily in so-called signet ring blood cells, has been successfully described [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Biologically ex...

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Section: Discussionmentioning

confidence: 99%

“…Unlike the case for P. nigra [19,28], however, aquated vanadyl ion is typically scarce in the blood cells of A. ceratodes [15,22,[29][30][31]. Nevertheless, tunicate blood cells can directly take up vanadium [32][33][34]. Thus, isolated A. ceratodes whole blood cells were incubated with DTT either alone or along with added inorganic vanadyl ion.…”

mentioning

confidence: 99%

The uptake and fate of vanadyl ion in ascidian blood cells and a detailed hypothesis for the mechanism and location of biological vanadium reduction. A visible and X-ray absorption spectroscopic study

Frank

Carlson²,

Carlson³

et al. 2008

Journal of Inorganic Biochemistry

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“…Uptake studies of 48 V showed that vanadium is primarily transported to the tunicate's blood plasma via the branchial sacs . Some additional absorption takes place in the gastrointestinal tract.…”

Section: 14 Uptake Of Vanadate Into Tunicatesmentioning

confidence: 99%

“…563 Uptake studies of 48 V showed that vanadium is primarily transported to the tunicate's blood plasma via the branchial sacs. 564 Some additional absorption takes place in the gastrointestinal tract. Vanadate enters the tunicates through anionic transporters as evidenced by the inhibition of vanadate uptake in the presence of phosphate, 565 but recently the existence of a vanadium transporter has been suggested (Figure 14).…”

Section: Uptake Of Vanadate Into Tunicatesmentioning

confidence: 99%