Mackay E A, Overnell J, Dunbar B, Davidson I, Hunziker P E, Kägi J H, Fothergill J E
Department of Molecular and Cell Biology, University of Aberdeen, Scotland.
Eur J Biochem. 1993 Nov 15;218(1):183-94. doi: 10.1111/j.1432-1033.1993.tb18364.x.
Cadmium-induced metallothioneins from the common sea mussel, Mytilus edulis, were shown to comprise of two groups of isoforms having apparent molecular masses of 10 kDa and 20 kDa. The 10-kDa group was resolved by anion-exchange chromatography into four fractions while the 20-kDa group was resolved into three fractions using this method. After metal removal and S-methylation of the cysteine residues using methyl-p-nitrobenzenesulphonate the complete amino acid sequences were determined. Five isoforms of the 20-kDa group were shown to possess monomeric units consisting of 71 amino acids. These proteins were distinct from the four 72-amino-acid proteins of the 10-kDa group. The FASTA algorithm has been used to compare the degree of similarity between the mussel metallothionein MT-10-IV isoform and other metallothioneins. The mussel MT-10-IV isoform exhibited substantial similarity to other molluscan metallothioneins. Moreover, the mussel metallothionein exhibited more similarity to vertebrate metallothioneins than to those of non-molluscan invertebrates, thus suggesting that the mussel metallothioneins are class I metallothioneins.
研究表明，从贻贝（紫贻贝）中提取的镉诱导金属硫蛋白由两组同工型组成，其表观分子量分别为10 kDa和20 kDa。通过阴离子交换色谱法，10 kDa组被分离为四个组分，而20 kDa组用该方法被分离为三个组分。在使用对硝基苯磺酸甲酯去除金属并对半胱氨酸残基进行S-甲基化后，测定了完整的氨基酸序列。结果显示，20 kDa组的五种同工型具有由71个氨基酸组成的单体单元。这些蛋白质与10 kDa组的四种由72个氨基酸组成的蛋白质不同。使用FASTA算法比较了贻贝金属硫蛋白MT-10-IV同工型与其他金属硫蛋白之间的相似程度。贻贝MT-10-IV同工型与其他软体动物金属硫蛋白表现出显著的相似性。此外，贻贝金属硫蛋白与脊椎动物金属硫蛋白的相似性高于与非软体动物无脊椎动物金属硫蛋白的相似性，因此表明贻贝金属硫蛋白属于I类金属硫蛋白。
