Characterization of metallothioneins (MT-I and MT-II) in yak

¹ College of Animal Science and Technology, Gansu Agricultural University, Lanzhou 730070
² College of Animal Science and Technology, Gansu Agricultural University, Lanzhou 730070; National Key Laboratory of Protein Engineering, Peking University, Beijing 100871; Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101
³ National Key Laboratory of Protein Engineering, Peking University, Beijing 100871
⁴ College of Life Sciences, Beijing Normal University, Beijing 100875
⁵ Grazinglands Research Laboratory, USDA-ARS, El Reno, OK 73036

^* To whom correspondence should be addressed. E-mail: renhw{at}pku.edu.cn.

	Abstract

The cDNA encoding sequences for yak metallothionein isoforms I (MT-I) and II (MT-II) were amplified and cloned by reverse transcriptase PCR to characterize nucleotide sequence and protein structure of metallothionein in yak. These cDNA sequences of MT-I and MT-II were subjected to BLASTn searching at the National Center for Biotechnology Information and the results indicated that the nucleotide sequences of yak MT-I and MT-II, when compared among different species of mammals are highly conservative. The yak open reading frames have a length of 183 nucleotides which encode for yak MT-I and MT-II proteins of 61 AA, respectively. Analysis of hydrophobicity, transmembrane region and signal peptides suggested that metallothioneins of yak are non-secretory proteins. There were several conserved tripeptide sequences, such as C-X-C, C-C-X-C-C and C-X-X-C (X designates AA excluding cysteine in MT-I and MT-II), and they are highly conserved in their evolution. By homologous comparative modeling, we have predicted the molecular spatial structures of yak MT-I and MT-II, which are composed of and domains that are linked by the conserved tripeptide LYS³⁰-LYS³¹-SER³² (KKS).

Key Words: cDNA, characterization, metallothioneins, structure, yak