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《Acta Zoologica Sinica》 2002-01
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LIN Zhi-Lan ① LI Fu-Rong ② MA Guo-Dong ① LIANG Shuang ① (①College of Life Sciences, Peking University, Beijing 100871, China) (②Department of Biology, Xinyang Teachers College, Xinyang 464000, Henan, China)  
Metallothioneins ( MTs ) are a group of low molecular weight, metal-binding and cysteine rich proteins. MTs are widely distributed throughout living organisms and are fairly well identified in mammals, amphibians, fishes, plants, fungi, and cyanobacteria. To compare with the MT's- character, the high degree of conservation of amino acid sequence and the central segments in MTs from many sources will provide significant information for investigation of MT's structure and function or the molecular evolution. Thus far, there are no reports for MT isolated from reptiles. In the present paper, we report the presence of MT from turtle liver. Each extract of Chinese soft-shelled turtle (Pelodiscus sinensis) liver after induction with subcutaneous injection of ZnSO 4, CuSO 4 or CdCl 2 was separated by gel filtration chromatography Sephadex G-50 column and subsequent DEAE Sepharose CL-6B, than Sephadex G-25 for desalination, respectively. According to the results of mass spectrometry and HPLC filtration chromatography detection, the molecular weight of the MT is shown to be about 6 300 dalton. The MT containing 61 amino acid residues has a high cysteine content (17%), aromatic amino acids (tyrosine, phenylalanine), arginine and histidine are considerably low. Zn-MT, Cu-MT or Cd-MT has an ultraviolet absorption shoulder near 220 nm, 270 nm or 250 nm, respectively. In the present work we show that the properties of turtle liver MT are similar to the mammals in molecular weight and cysteine residues of MT. However, the other properties (including the amino acid composition of MT and the capability of binding metal ions) are similar to the MT from the earthworm and yeast. The characteristic of MT in turtle lies between the MT of mammals and lower living organisms. This result presents the distinguishing characteristics of biological evolution of MT in turtle.
【Fund】: 国家自然科学基金资助项目 (No .39370 0 2 1)~~
【CateGory Index】: Q51
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