【摘要】 金属硫蛋白是一种普遍存在于生物体内的低分子量、半胱氨酸含量丰富、易于被外界刺激诱导的金属结合蛋白。采用表达序列标签法,结合cDNA末端快速扩增技术,首次获得了海湾扇贝金属硫蛋白(AiMT)的全长cDNA序列。该序列全长787bp,5′UTR(UntranslatedRegion)为79bp,3′UTR为270bp,开放阅读框(OpenReadingFrame,ORF)长度为438bp,可编码145个氨基酸。在其编码的氨基酸序列中半胱氨酸含量丰富,甘氨酸含量也较高,芳香族氨基酸含量低,不含组氨酸,存在有无脊椎动物和软体动物金属硫蛋白的特征序列CKCXXX-CXCX,C-末端的氨基酸序列也符合软体动物金属硫蛋白标签序列C-x-C-x(3)-C-T-G-x(3)-C-x-C-x(3)-C-x-C-K。序列特征分析表明,该序列具备金属硫蛋白的典型特征,是金属硫蛋白家族的成员。更多还原

【Abstract】 Metallothioneins(MTs)are low molecular weight, cysteine-rich, inducible metal-binding proteins found in a variety of organisms. MTs have many important biological functions acted as a protective role against excess reactive heavy metal ions, free radical scavengers and reservoir of essential metals that can be donated to other metalloproteins. A partial sequence of the bay scallop Argopecten irradians metallothionein(named as AiMT)gene was identified from A. irradians cDNA library using expressed sequence tag method. A pair of gene-specific primers was designed according to this sequence and the full-length of AiMT cDNA was obtained using rapid amplification of cDNA end technique. The full-length cDNA of AiMT was of 787bp including a 5′untranslated region(UTR)of 79bp, a 3′UTR of 270 bp and an open reading frame(ORF)of 438bp encoding a polypeptide of 145 amino acids. The predicted amino acid sequence of AiMT contained 40 cysteine residues organized in Cys-X (n)-Cys(n=1—3)motif as classically described for MTs. The contents of cysteine, glycine and phenylalanine in the AiMT amino acids sequence were 27.6%, 13.1% and 2.1% respectively while no histidine residue was found. The CKCXXXCXCX motif, a conserved feature for invertebrate and molluscan MT, was found in two regions of the AiMT. A specific pattern of mollusca MT C-x-C-x(3)-C-T-G-x(3)-C-x-C-x(3)-C-x-C-K located at the C-terminal. The result of sequence analysis indicated that AiMT was the member of metallothionein family.更多还原