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水稻类金属硫蛋白(rgMT)的两端是高度保守的半胱氨酸富含区的结构域(CR区),中间是不含半胱氨酸的间隔区,呈典型的三段式结构。本研究分别采用距离几何算法和同源建模相结合的方法对水稻类金属硫蛋白进行三级结构建模。在排列出CR区的所有可能的半胱氨酸-金属硫络合的组合方式,并对每一种组合方式给出一定的限制条件后各生成20个随机构象。根据生成的随机构象是否能形成金属硫络合结构,从900个随机构象中最终选出6个构象(N端4种,C端2种组合)作为可能的结构模型。另一方面,采用GOR方法对间隔区进行了二级结构预测,随后用同源建模法对其建模。将上述建成的三部分模型连接起来后形成rgMT的整体三维构象。结果表明rgMT能像哺乳动物MT蛋白一样,可形成两个独立的、在结构和能量上均没有障锝的金属-硫络合结构。介于所有植物类金属硫蛋白都具有典型的三段式结构,其中的一部分还具有与rgMT相同的半胱氨酸排列方式,所以rgMT三维结构模型的建立对于其他植物类金属硫蛋白的结构研究具有重要的参考价值。
Both ends of rice metallothionein (rgMT) are highly conserved cysteine-rich domains (CR regions) with a cysteine-free spacer in the middle and a typical three-segment structure. In this study, the three-level structure of metallothionein in rice was modeled by distance geometry and homology modeling respectively. Twenty random conformations were generated after all the possible cysteine-metal sulfur complexes in the CR region were aligned and given the constraints for each combination. Depending on whether the generated random conformation can form a metal sulfur complex structure, six conformations (N-terminal 4, C-terminal 2 combinations) are finally selected from 900 random conformations as possible structural models. On the other hand, the GOR method was used to predict the secondary structure of the spacer region and then was modeled by homology modeling. The three-part model built above is connected to form the overall three-dimensional conformation of rgMT. The results indicate that rgMT, like the mammalian MT protein, forms two independent metal-sulfur complexes that have no barrier technetium in structure and energy. Since all phyto-metallothioneins have a typical three-staged structure and some of them also have the same cysteine arrangement as rgMT, the establishment of the rgMT three-dimensional structural model has been used to study the structure of other plant metallothioneins Has important reference value.