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ID 15045
file
creator
Kawakami, Norifumi
Gekko, Kunihiko
Michibata, Hitoshi
subject
Ascidian
Copper
Metal selectivity
Metal-binding protein
Vanadium
NDC
Physics
abstract
Vanadium-binding proteins, or Vanabins, have recently been isolated from the vanadium-rich ascidian, Ascidia sydneiensis samea. Recent reports indicate that Vanabin2 binds twenty V(IV) ions at pH 7.5, and that it has a novel bow-shaped conformation. However, the role of Vanabin2 in vanadium accumulation by the ascidian has not yet been determined. In the present study, the effects of acidic pH on selective metal binding to Vanabin2 and on the secondary structure of Vanabin2 were examined. Vanabin2 selectively bound to V(IV), Fe(III), and Cu(II) ions under acidic conditions. In contrast, Co(II), Ni(II), and Zn(II) ions were bound at pH 6.5 but not at pH 4.5. Changes in pH had no detectable effect on the secondary structure of Vanabin2 under acidic conditions, as determined by circular dichroism spectroscopy, and little variation in the dissociation constant for V(IV) ions was observed in the pH range 4.5-7.5, suggesting that the binding state of the ligands is not affected by acidification. Taken together, these results suggest that the reason for metal ion dissociation upon acidification is attributable not to a change in secondary structure but, rather, that it is caused by protonation of the amino acid ligands that complex with V(IV) ions.
journal title
Biochimica et Biophysica Acta - General Subjects
volume
Volume 1760
issue
Issue 7
start page
1096
end page
1101
date of issued
2006-07
publisher
Elsevier B.V.
issn
0304-4165
ncid
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
author
rights
Copyright (c) 2006 Elsevier B.V.
relation is version of URL
http://dx.doi.org/10.1016/j.bbagen.2006.03.013
department
Graduate School of Science



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