炭疽保护性抗原受体结合区的关键氨基酸位点分析

目的 分析炭疽毒素保护性抗原（PA）受体结合区与其功能相关的关键氨基酸位点。方法通过定点突变的方法将PA的Asp^683分别突变成为一系列带有不同电荷以及不同长度侧链的氨基酸，通过细胞毒性实验分别探询电荷及立体结构对其活性的影响。同时对Asp^683的一些邻近氨基酸进行了定点突变的研究。结果细胞毒性实验显示，不同的突变导致了PA活性不同程度的下降，其中Asp^683电荷的改变对其活性的影响尤为明显，但当它突变为不带电荷的氨基酸时，PA仍然保留了一定的活性；而当Asp^683突变为带正电的Lys后，PA却保留了相对较高的活性。结论Asp^683所带的负电荷在PA与其受体的相互作用中起着关键的作用，但PA与其受体之间的相互作用可能还通过一些其他方式进行。

Analysis of key amino acids of the Bacillus anthracis protective antigen receptor-binding region

Objective To analyze the key amino acids of the Bacillus anthracis protective antigen(PA) receptor-binding region. Methods Asp~683 was converted into a series of other amino acids by site-directed mutagenesis. Substituted PA proteins were analyzed by cellular cytotoxicity assays to study the influence of charge or dimensional structure of the acid. Furthermore, some variants with neighbor amino acids of Asp~683 were constructed and analyzed by the same way. Results BResults of the cellular cytotoxicity assays showed that different mutations gave rise to different extents of decrease in its toxicity. The influence of the change of related negative charge of Asp~683 was especially evident while Asp~683 was converted into electropositive Lys, it still kept some toxicity. Conclusion The negative charge of Asp~683 plays a very crucial role in the interaction between PA and its receptor, though other mechanisms are potentially present.