Metal binding ability of glutathione transferases conserved between two animal species, the vanadium-rich ascidian Ascidia sydneiensis samea and the schistosome Schistosoma japonicum.
Glutathione transferases (GSTs) are multifunctional enzymes found in many organisms. We recently identified vanadium-binding GSTs, designated AsGSTs, from the vanadium-rich ascidian, Ascidia sydneiensis samea. In this study, the metal-selectivity of AsGST-I was investigated. Immobilized metal ion affinity chromatography (IMAC) analysis revealed that AsGST-I binds to V(IV), Fe(III), and Cu(II) with high affinity in the following order Cu(II)>V(IV)>Fe(III), and to Co(II), Ni(II), and Zn(II) with low affinity. The GST activity of AsGST-I was inhibited dose-dependently by not V(IV) but Cu(II). A competition experiment demonstrated that the binding of V(IV) to AsGST-I was not inhibited by Cu(II). These results suggest that AsGST-I has high V(IV)-selectivity, which can confer the specific vanadium accumulation of ascidians. Because there are few reports on the metal-binding ability of GSTs, we performed the same analysis on SjGST (GST from the schistosome, Schistosoma japonicum). SjGST also demonstrated metal-binding ability although the binding pattern differed from that of AsGST-I. The GST activity of SjGST was inhibited by Cu(II) only, as that of AsGST-I. Our results indicate a possibility that metal-binding abilities of GSTs are conserved among organisms, at least animals, which is suggestive of a new role for these enzymes in metal homeostasis or detoxification.
Yoshinaga
Masafumi
M
Molecular Physiology Laboratory, Department of Biological Science, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan.
Ueki
Tatsuya
T
Michibata
Hitoshi
H
D000818:Animals; D002846:Chromatography, Affinity; D005982:Glutathione Transferase / Q000378:metabolism*; D008670:Metals / Q000378:metabolism*; D012549:Schistosoma japonicum / Q000201:enzymology*; D014561:Urochordata / Q000201:enzymology*; D014639:Vanadium / Q000378:metabolism
D008670:Metals; D014639:Vanadium; D005982:Glutathione Transferase