Shark (Scyliorhinus torazame) metallothionein: cDNA cloning, genomic sequence, and expression analysis.
Novel metallothionein (MT) complementary DNA and genomic sequences were isolated from a cartilaginous shark species, Scyliorhinus torazame. The full-length open reading frame (ORF) of shark MT cDNA encoded 68 amino acids with a high cysteine content (29%). The genomic ORF sequence (932 bp) of shark MT isolated by polymerase chain reaction (PCR) comprised 3 exons with 2 interventing introns. Shark MT sequence shared many conserved features with other vertebrate MTs: overall amino acid identities of shark MT ranged from 47% to 57% with fish MTs, and 41% to 62% with mammalian MTs. However, in addition to these conserved characteristics, shark MT sequence exhibited some unique characteristics. It contained 4 extra amino acids (Lys-Ala-Gly-Arg) at the end of the beta-domain, which have not been reported in any other vertebrate MTs. The last amino acid residue at the C-terminus was Ser, which also has not been reported in fish and mammalian MTs. The MT messenger RNA levels in shark liver and kidney, assessed by semiquantitative reverse transcriptase PCR and RNA blot hybridization, were significantly affected by experimental exposures to heavy metals (cadmium, copper, and zinc). Generally, the transcriptional activation of shark MT gene was dependent on the dose (0-10 mg/kg body weight for injection and 0-20 microM for immersion) and duration (1-10 days); zinc was a more potent inducer than copper and cadmium.
Cho
Young Sun
YS
Department of Aquaculture, Pukyong National University, Busan, 608-737, South Korea.
Choi
Buyl Nim
BN
Ha
En-Mi
EM
Kim
Ki Hong
KH
Kim
Sung Koo
SK
Kim
Dong Soo
DS
Nam
Yoon Kwon
YK
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D016000:Cluster Analysis; D015870:Gene Expression; D015723:Gene Library; D008668:Metallothionein / Q000235:genetics* / Q000378:metabolism*; D019216:Metals, Heavy / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012754:Sharks / Q000235:genetics* / Q000378:metabolism
D019216:Metals, Heavy; D008668:Metallothionein