一种新型结构的金属硫蛋白──Pb-MT'

A Novel Structure Motif of Metallothionein PbMT

金属硫蛋白（ｍｅｔａｌｏｔｈｉｏｎｅｉｎｓ，简称ＭＴｓ）是一大类富含巯基的小分子蛋白质（分子量＜９０００），具有很强的金属结合能力，哺乳动物ＭＴ每分子可结合７个二价金属离子或１２个一价金属离子．ＭＴ的结构一直是科学家关注的热点，其中哺乳动物Ｃｄ７－Ｍ...

Lead()binding behaviors of rabbit liver thionein2(apoMT2) has been studied by monitoring the changes of their electronic absorption(UV) and circular dichroism(CD) spectra. Two MT species, Pb7MT and Pb7MT, are observed upon the binding of Pb to apoMT at different pH. The formation of Pb7MT or Pb7MT is closely realted to the amount of deprotoned sulfhydryl groups. Pb7MT is formed only at high pH characterized by UV 340 nm shoulder and CD 245 nm band. Then the formation of a new leadmetallothionein complex, namely PbMT, is observed at low pH (pH<6). This new species is characterized by a strong circular dichroism(CD) cotton effect at 395 nm(-), 310 nm(-) peaks and 350 nm(+), 250 nm(+) doublehump and a unique electronic absorption(UV) spectrum at 325 nm, 375 nm and 400 nm shoulder. From their characteristic peaks in UV and CD spectra, it is deduced that Pb\+2+ in Pb7MT is coordinated by four sulfhydryl groups in Td microsymmetry, while multiple Pb\+2+ coordination including twocoordination mayb