title: Functional comparison of metallothioneins MTT1 and MTT2 from Tetrahymena thermophila.
abstract: Metallothioneins MTT1 and MTT2 from Tetrahymena thermophila have been characterized. The MTT1 contains mainly characteristic Cys-Cys-Cys and Cys-Cys clusters, but MTT2 contains mainly Cys-X-Cys cluster. Cd(16)-MTT1 mainly consists of α-helix and β-turns, in contrast, Cd(11)-MTT2 mainly consists of random coils. Reaction of Cd(16)-MTT1 and Cd(11)-MTT2 with nitric oxide leads to intramolecular disulfide bond formation, respectively. Binding stabilities of Cd(2+), Hg(2+) and Zn(2+) to MTT1 are stronger than those to MTT2. Cu(2+) can not replace Cd(2+) from Cd(16)-MTT1 complex, but can replace Cd(2+) from Cd(11)-MTT2 complex. The analysis of qRT-PCR revealed MTT2 mRNA levels were 31-fold higher than those of MTT1 under basal conditions. These results further suggest MTT1 possibly play a role in the detoxification of heavy metal ions, and MTT2 may be involved in the homeostasis of copper ions.
authors.affiliation: Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Biotechnology, Shanxi University, Taiyuan 030006, PR China.
authors.forename: Qinglu
authors.initials: Q
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.forename: Baofeng
authors.initials: B
authors.lastname: Chai
authors.forename: Aihua
authors.initials: A
authors.lastname: Liang
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D000975:Antioxidants / Q000378:metabolism; D002104:Cadmium / Q000378:metabolism; D003300:Copper / Q000378:metabolism; D015870:Gene Expression; D008628:Mercury / Q000378:metabolism; D008668:Metallothionein / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016415:Sequence Alignment; D016808:Tetrahymena thermophila / Q000235:genetics / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism
chemical_list: D000975:Antioxidants; D015800:Protozoan Proteins; D002104:Cadmium; D003300:Copper; D008668:Metallothionein; D008628:Mercury; D015032:Zinc