Cloning, expression, and characterization of cadmium-induced metallothionein-2 from the earthworms Metaphire posthuma and Polypheretima elongata

Shih Hsiung Liang, Yu Ping Jeng, Yuh Wen Chiu, Jiun Hong Chen, Bao Sen Shieh, Chien Yen Chen, Chien Cheng Chen

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

In this study we report the sequences of MT-2 cDNA from two species of Megascoleidae earthworms, Metaphire posthuma and Polypheretima elongata, by mRNA differential display after exposure of the organisms to cadmium. Complementary (c)DNA was verified as the MT-2 gene by the characteristics of its predicted translation product, namely a high cysteine content, conserved CXC motifs, and a molecular weight of around 8 kDa. Amino acid sequence alignment revealed a conserved TKCCG in the cloned MT-2 of both megascolecid earthworms instead of the corresponding conserved TQCCG found in lumbricid earthworms. The cDNAs corresponding to the two megascolecid MT-2 genes were expressed, and the MT-2 proteins were purified for biochemical characterization. The binding of Cu2+ exhibited monophasic kinetics and those of Zn2+ and Cd2+ biphasic kinetics. The proteins bound more tightly to Cd2+ than to Zn2+ and more tightly still to Cu2+. Zn-MT and apo-MT were the most effective at scavenging free radicals, followed by Cd-MT. In conclusion, MT-2s from M. posthuma and P. elongata showed unique sequence features compared to those of lumbricid earthworms. These earthworms could be used to evaluate heavy-metal pollution in soil due to the inducible MT-2 by cadmium exposure.

Original languageEnglish
Pages (from-to)349-357
Number of pages9
JournalComparative Biochemistry and Physiology - C Toxicology and Pharmacology
Volume149
Issue number3
DOIs
Publication statusPublished - 2009 Apr

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Physiology
  • Toxicology
  • Cell Biology
  • Health, Toxicology and Mutagenesis

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