Squalene and oxidosqualene cyclizations are regarded as the most complex chemical reactions in the nature,which can achieve protonation,deprotonation,a sequence of hydride and methyl migration. Dammarenediol-Ⅱ synthase( DS),as a kind of 2,3-oxidosqualene-triterpene cyclase,catalyses2,3-oxidosqualene to form dammarenediol-Ⅱ. To assess the three-dimensional( 3 D) structure and catalytic active sites of dammarenediol-Ⅱ synthase,utilizing the homology modeling method,3 D models of DS were established in the Modeller9 v14 software and I-TASSER server. With the highest sequence identity with DS,human oxidosqualene cyclase 3 D models( PDB: 1 W6K and 1 W6J) were chosen as templates. Through further evaluation and optimization,an optimal DS model was obtained consequently. Then several putative catalytic active sites were found through the molecular docking simulation between DS model and product dammarenediol-Ⅱ by using Autodock 4. 2. Finally,site-directed mutants of DS were expressed in Saccharomyces cerevisiae,a significant decrease of the yield of dammarenediol-Ⅱ is achieved,which verified the significance of these putative active sites.
Mitochondrial DNA(mt DNA)mutations have been implicated in a broad range of disorders which severely affect human health(Wallace,1999).Some drugs have been developed to slow down pathological changes of mitochondrial disorders.However,there is no effective treatment for patients with mt DNA mutations.mt DNA is less protected and has fewer repair mechanisms than nuclear DNA(n DNA).Such a reality results in a much higher
Liang YangTingfang MeiXiaobing LinHaite TangYi WuRui WangJinglei LiuZahir ShahXingguo Liu
