广西植物2017，Vol.37Issue(3)：373-379,387,8.DOI:10.11931/guihaia.gxzw201601035
甜瓜鲨烯合酶基因克隆及酶分子结构分析
Gene cloning and molecular characteristics of squalene synthase from Cucumis melo
摘要
Abstract
Cucurbitacins (Cus) are tetracyclic triterpenoid compounds which exist mainly in cucurbitaceous plants and have various pharmaceuticals-like actions.The medicinal raw materials of Cus are currently extracted mainly from the pedicellus melo.In this study, the gene of squalene synthase (SQS), the key enzyme for Cus biosynthesis, from Cucumis melo was cloned, and the amino acid sequence of the enzyme derived from its nucleotide sequence was analyzed with bioinformatics methods.DNA sequencing and BLAST RefSeqGene analysis indicated that the cloned fragment of the C.melo SQS gene contained a complete open reading frame (ORF) of the gene.ORF Finder analysis showed that the SQS of C.melo was constituted of 417 amino acid residues with an isoelectric point of 7.56.Analysis of the deduced amino acid sequence suggested that the main type of secondary structure of the enzyme was α helix.Domain prediction study indicated that the SQS belonged to the isoprenoid biosynthase superfamily possessing the banding sites of farnesyl diphosphate and magnesian ion.Prediction of the tertiary structure suggested that the SQS was a monomeric enzyme with a cave-like activity center formed by α helixes.Protein phosphorylation analysis indicated that the phosphorylation site S48 located in the activity center-related motif 47 VSRSF52 and S196 was a positive selection site, suggesting that both S48 and S196 were critical sites for the regulation of SQS activity.The phylogenetic classification based on the phylogenetic tress constructed with the ORF sequence of the SQS gene showed that the result was in accordance with that of morphologic classification.Therefore, this study provides new clues and reference for research of the regulation of Cus biosynthesis.关键词
甜瓜/鲨烯合酶/基因克隆/序列分析Key words
Cucumis melo/squalene synthase/gene cloning/sequence analysis分类
农业科技引用本文复制引用
黄海霞,苏何玲,史云龙,肖雅伦,谭燕莲,梁杨浩,刘永明,吴耀生..甜瓜鲨烯合酶基因克隆及酶分子结构分析[J].广西植物,2017,37(3):373-379,387,8.基金项目
国家自然科学基金(31260069)；广西高等学校优秀中青年骨干教师培养工程项目 [Supported by the National Natural Science Foundation of China (31260069) （31260069）
the Training Program of the Outstanding Higher Education Teachers of Guangxi from by the Education Department of Guanxi Zhuang Autonomous Region]。 （）
