Wang Jia, Zhang Li-Ping, Yang Lian, Fei Chun-Hong, Wang Lei, Xie Chao, Wu Jian-Ping
Faculty of Animal Science and Technology, Gansu Agricultural University, Lanzhou, 730070, China.
Yi Chuan. 2008 Dec;30(12):1591-6. doi: 10.3724/sp.j.1005.2008.01591.
Metallothioneins (MTs) was characterized by its low molecular weight (6 to 7 kDa), high metal content, high content of conserved cysteine(Cys) residues and absence of aromatic amino acids. In mammals there are four isoforms (MT-I-IV), MT-IV was expressed exclusively in stratified squamous epithelia. In this study, according to other animal MT-IV gene sequence from GenBank, a pair of special primers (MT-IVSP1 and MT-IVSP2) were designed for cloning the coding sequence of MT-IV from rumen organ in both sheep and goat. The MT-IV coding sequence in goat and sheep were 189bp, and be submitted to GenBank under Accession Numbers EF470251 and EF624067, respectively. Both goat and sheep MT-IV gene coded 62 AAs, including 20 Cys residues in sheep, 19 Cys residues in goat, the 61st conserved Cys was replaced by Trp in goat. MT-IV in goat and sheep both have characteristic Cys-x-Cys, Cys-x-y-Cys, and Cys-Cys sequences of MTs , where x and y were non-cysteine amino acids, no aromatic AAs, no cross membrane area, and no signal peptide, these information showed MT-IV in goat and sheep was a cytoplasmic protein. The second structure of MT-IV was coil, except sheet structure in 7-9 AAs and 49-51AAs. The 3 dimension structure was composed by a-and b-domain, the beta-domain structure was same between sheep and goat, and same with other species, but a- domain structure in goat was difference with sheep and other species, because it less one Cys in goat than other animals,the structure change maybe alter the biological function, it is necessary to study further.
金属硫蛋白（MTs）的特点是分子量低（6至7千道尔顿）、金属含量高、保守半胱氨酸（Cys）残基含量高且不含芳香族氨基酸。在哺乳动物中有四种亚型（MT-I-IV），MT-IV仅在复层鳞状上皮中表达。在本研究中，根据GenBank中其他动物的MT-IV基因序列，设计了一对特异性引物（MT-IVSP1和MT-IVSP2），用于从绵羊和山羊的瘤胃器官中克隆MT-IV的编码序列。山羊和绵羊的MT-IV编码序列均为189bp，分别以登录号EF470251和EF624067提交至GenBank。山羊和绵羊的MT-IV基因均编码62个氨基酸，其中绵羊有20个Cys残基，山羊有19个Cys残基，山羊的第61个保守Cys被色氨酸取代。山羊和绵羊的MT-IV均具有MTs特有的Cys-x-Cys、Cys-x-y-Cys和Cys-Cys序列，其中x和y为非半胱氨酸氨基酸，无芳香族氨基酸，无跨膜区域，无信号肽，这些信息表明山羊和绵羊的MT-IV是一种细胞质蛋白。MT-IV的二级结构为卷曲状，7-9位氨基酸和49-51位氨基酸处除外，此处为片状结构。三维结构由α结构域和β结构域组成，绵羊和山羊的β结构域结构相同，与其他物种也相同，但山羊的α结构域结构与绵羊及其他物种不同，因为山羊比其他动物少一个Cys，这种结构变化可能会改变生物学功能，有必要进一步研究。
