Analysis of the proteins possessed by the last common ancestor and the organisms present before it

我们复活了细菌和古细菌共同祖先所具有的核苷酸二磷酸激酶（NDK）基因，并分析了复活基因产生的蛋白的热稳定性。祖先的NDK在接近110摄氏度时表现出稳定性，这表明细菌和古细菌的共同祖先在80到100摄氏度之间的温度下茁壮成长。最后的共同祖先commonote的NDK也复活并繁殖。祖先的NDK显示出高稳定性，表明普通鼹鼠生活在75摄氏度或更高的温度下。从20个氨基酸种中剔除1个的NDKs序列，对其稳定性和活性进行了分析。结果表明，氨基酸的种类并不是稳定性和活性所必需的。

We have resurrected the gene of the nucleotidediphosphate kinase (NDK) possessed by the common ancestor of Bacteria and Archaea, and analyzed the thermal stability of the protein produced from the resurrected genes. The ancestral NDKs showed stability close to 110 degree C, suggesting the common ancestors of Bacteria and Archaea were thriving at the temperature between 80 and 100 degree C. The NDK of the last common ancestor, commonote, was also resurrected and reproduced. The ancestral NDK showed the high stability, suggesting that the commonote were living at 75 degree C or higher temperature. The ancestral NDKs from which one of the 20 amino acid species were removed, were produced and whose stability and activity were analyzed. The results showed the amino acid species that is not absolutely required for the stability and activity.