[关键词]
[摘要]
目的 构建川芎咖啡酸-3-O-甲基转移酶(Ligusticum chuanxiong caffeic acid-3-O-methyltransferase,LCCOMT)的三维模型,并利用定点突变对模型进行验证。方法 利用同源建模构建LCCOMT的初始三维模型;对初始三维模型进行动力学优化;将优化后的模型对接咖啡酸,预测LCCOMT的活性位点;对预测的活性位点展开定点突变,检测突变型蛋白的生物活性。结果 LCCOMT的三维模型能够与咖啡酸成功对接,His268残基可能是LCCOMT的活性位点,推测其能够与咖啡酸3-OH形成氢键。H268N与H268Q 2种突变酶分别丧失94.85%和95.28%的催促活性。结论 同源建模能够准确预测LCCOMT的三维模型。His268为LCCOMT的关键氨基酸残基,其作用可能是作为共轭碱,参与咖啡酸3-OH的去质子化反应。
[Key word]
[Abstract]
Objective To construct the three dimensional models of L. chuanxiong caffeic acid-3-O-methyltransferase (LCCOMT) and verify the model using site-directed mutagenesis technology. Methods The three-dimensional model was constructed by homology modeling using the crystal structure of COMT from Medicago sativa as a temple. Caffeic acid was docked into the optimized model of LCCOMT to predict the active site. The predicted site was mutated using site-directed mutagenesis technology. Then, the activity of mutant enzyme was detected. Results The molecular docking, which showed there were hydrogen bonds between His268 and 3-OH of caffeic acid, was successful. Two mutant enzymes, H268N and H268Q, lost 94.85% and 95.28% of their activity respectively. Conclusion The His268 is confirmed as one of the key residues of LCCOMT. It may play a role as a base in the deprotonation reaction of the 3-OH of caffeic acid.
[中图分类号]
[基金项目]
国家自然科学基金资助项目(31371232,31500276);成都市科技技术研发项目(2015-HM01-00051-SF);国家级大学生创新创业训练计划资助项目(201510613063)