Wu J P, Ma B Y, Ren H W, Zhang L P, Xiang Y, Brown M A
College of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China 730070.
J Anim Sci. 2007 Jun;85(6):1357-62. doi: 10.2527/jas.2006-291. Epub 2006 Nov 22.
The cDNA-encoding sequences for yak metallothionein isoforms I (MT-I) and II (MT-II) were amplified and cloned by reverse-transcription PCR to characterize the nucleotide sequence and protein structure of metallothionein in the yak. The cDNA sequences of MT-I and MT-II were subjected to BLAST 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 conserved. 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, trans-membrane region, and signal peptides suggested that metallothioneins of the yak are nonsecretory 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 predicted the molecular spatial structures of yak MT-I and MT-II, which are composed of alpha- and beta-domains that are linked by the conserved tripeptide Lys(30)-Lys(31)-Ser(32) (KKS).
通过逆转录PCR扩增并克隆了牦牛金属硫蛋白同工型I（MT-I）和II（MT-II）的cDNA编码序列，以表征牦牛金属硫蛋白的核苷酸序列和蛋白质结构。将MT-I和MT-II的cDNA序列在美国国立生物技术信息中心进行BLAST搜索，结果表明，与不同种类的哺乳动物相比，牦牛MT-I和MT-II的核苷酸序列高度保守。牦牛的开放阅读框长度为183个核苷酸，分别编码61个氨基酸的牦牛MT-I和MT-II蛋白。对疏水性、跨膜区域和信号肽的分析表明，牦牛的金属硫蛋白是非分泌蛋白。存在几个保守的三肽序列，如C-X-C、C-C-X-C-C和C-X-X-C（X表示MT-I和MT-II中除半胱氨酸外的氨基酸），它们在进化过程中高度保守。通过同源比较建模，我们预测了牦牛MT-I和MT-II的分子空间结构，它们由通过保守三肽Lys(30)-Lys(31)-Ser(32)（KKS）连接的α-和β-结构域组成。
