title: Two metallothioneins in the fresh-water fish, crucian carp (Carassius cuvieri): cDNA cloning and assignment of their expression isoforms.
abstract: Two metallothionein cDNAs (MT-A and MT-B) in the fresh-water fish crucian carp (Carassius cuvieri Temminck et Schlegel) were cloned. Sequence analysis of both cDNAs gave the structure of a coding region corresponding to 60 amino acid residues. The homology of their deduced amino acid sequences was completely conserved at the positions of the cysteine residue, but a significant difference existed in the size of their 3'-untranslated regions (130 base pairs for MT-A and 280 base pairs for MT-B). Direct amino acid sequencing of the MT-II isoform purified by HPLC was accomplished for up to 30 residues and its sequence was identical to that deduced from MT-B cDNA. This is the first case in vertebrates that N-terminal methionine in crucian carp MT-II was not blocked. By northern blot analysis, basal and cadmium chloride- or dexamethasone-induced MT-B (MT-II) mRNAs were detected time dependently after treatment. On the other hand, the expression of MT-A mRNA was extremely low. These results indicate that the MT isoform II in crucian carp is coded by the MT-B gene, and that the MT-B-dominant expression of mRNA in crucian carp may be due to the difference in the 3'-untranslated regions of MT mRNAs.
authors.affiliation: Department of Toxicology, Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan.
authors.forename: H W
authors.initials: HW
authors.lastname: Ren
authors.forename: N
authors.initials: N
authors.lastname: Itoh
authors.forename: M
authors.initials: M
authors.lastname: Kanekiyo
authors.forename: S
authors.initials: S
authors.lastname: Tominaga
authors.forename: J
authors.initials: J
authors.lastname: Kohroki
authors.forename: G S
authors.initials: GS
authors.lastname: Hwang
authors.forename: T
authors.initials: T
authors.lastname: Nakanishi
authors.forename: N
authors.initials: N
authors.lastname: Muto
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002347:Carps / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000096:biosynthesis* / Q000235:genetics; D005399:Fishes; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D008099:Liver / Q000201:enzymology; D008668:Metallothionein / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D051379:Mice; D008969:Molecular Sequence Data; D051381:Rats; D013045:Species Specificity
chemical_list: D018076:DNA, Complementary; D007527:Isoenzymes; D008668:Metallothionein