title: Identification and expression of a novel class of glutathione-S-transferase from amphioxus Branchiostoma belcheri with implications to the origin of vertebrate liver.
abstract: Glutathione-S-transferases have been identified in all the living species examined so far, yet little is known to date about them in amphioxus, a model organism for insights into the origin and evolution of vertebrates. We have isolated a cDNA encoding an amphioxus (Branchiostoma belcheri) glutathione-S-transferase with a predicted molecular mass of approximately 26 kDa, from the gut cDNA library. The glutathione-S-transferase had 43.7-51.8% identity to most glutathione-S-transferases identified from aquatic organisms including fish and green alga, but it was much less identical (<27%) to other cytosolic glutathione-S-transferase classes. The phylogenetic analysis revealed that the glutathione-S-transferase was grouped together with most piscine and algal glutathione-S-transferases, separating from other cytosolic glutathione-S-transferase classes. Moreover, the glutathione-S-transferase had an exon-intron organization typical of zebrafish putative GST, red sea bream GSTR1 and plaice GSTA1 genes. The recombinant glutathione-S-transferase has been successfully expressed and purified, which showed a relatively high catalytic activity (3.37+/-0.1 unit/mg) toward 1-chloro-2, 4-dinitrobenzene and a moderate activity toward ethacrynic acid (0.41+/-0.01 unit/mg), although it had no detectable activity toward 1, 2-dichloro-4-nitrobenzene, 4-hydroxynonenal, 4-nitrobenzyl chloride and cumene hydroperoxide. In addition, we have revealed a tissue-specific expression pattern of the glutathione-S-transferase gene in B. belcheri, with the most abundant expression in the hepatic caecum. All these indicate that the amphioxus glutathione-S-transferase belongs to a novel rho-class of glutathione-S-transferases with a tissue-specific expression pattern. The relation between the glutathione-S-transferase expression in amphioxus hepatic caecum and the origin of vertebrate liver is also discussed.
authors.affiliation: Department of Marine Biology, Ocean University of China, Qingdao 266003, China.
authors.forename: Chunxin
authors.initials: C
authors.lastname: Fan
authors.forename: Shicui
authors.initials: S
authors.lastname: Zhang
authors.forename: Zhenhui
authors.initials: Z
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.forename: Jing
authors.initials: J
authors.lastname: Luan
authors.forename: Gaowa
authors.initials: G
authors.lastname: Saren
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000918:Antibody Specificity; D002816:Chordata, Nonvertebrate / Q000033:anatomy & histology / Q000201:enzymology* / Q000235:genetics*; D018076:DNA, Complementary; D015870:Gene Expression; D005982:Glutathione Transferase / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D016415:Sequence Alignment; D014714:Vertebrates / Q000033:anatomy & histology / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D011994:Recombinant Proteins; D005982:Glutathione Transferase