Experimental verification of acquisition of hemoprotein high-order functions by reverse molecular evolution

在已有的蛋白质序列数据库的基础上，我们构建了肌红蛋白的系统发育树，并推测了两种祖先动物的肌红蛋白的氨基酸序列，一种是哺乳动物，另一种是鱼类(反向进化)。这些在大肠杆菌中合成的祖先肌红蛋白与相应的现存邻近动物北美负鼠和斑马鱼相比，具有高的氧亲和力、稳定的结构和较低的自氧化速率。因此，在哺乳动物和鱼类中，肌红蛋白已经进化到以牺牲结构稳定性和自氧化为代价的氧结合功能来适应环境。

On the basis of the sequence database for proteins now available, we constructed phylogenetic trees for myoglobin and inferred the amino acid sequences for two ancestor animal's myoglobins, one for mammalian and the other for fishes (reverse evolution). These ancestral myoglobins, synthesized in E. coli, showed high oxygen affinity, stable structure and lowered autooxidation rate compared to the corresponding extant neighbor animals, North American opossum and Zebra fish. Thus, it is considered that, in mammals and fishes, myoglobin has evolved so that oxygen binding function is adapted to environments at the sacrifice of structural stability and autooxidation.