以萝芙木叶片为材料,应用RT-PCR方法首次克隆了萝芙木萜类吲哚生物碱(terpeno id indo le a lka lo ids,T IA s)生物合成途径中重要的限速酶——异胡豆苷合成酶(strictos id ine syn thase,STR)基因(G enB ank登录号DQ 0170054)并进行了生物信息学分析,以pCAM B IA 1304为基本载体构建其植物高效表达载体pCAM B IA 1304+-R vSTR.生物信息学分析表明,该基因的编码区长度为1 035 bp,编码344个氨基酸的多肽,其理论分子量为38.2kD,等电点为5.2,N-端有一长度为27个氨基酸的信号肽;二级结构预测表明,延伸链和不规则盘绕是R vSTR蛋白最大量的结构元件,而α-螺旋和β-转角则散布于整个蛋白质中.同源性分析表明,R vSTR和其它植物来源的STR同源;采用M EGA 3构建了具代表性的植物STR的分子系统发育树,首次提出植物来源的STR分为2种类型,即STR 1和STR 2,其中来源于能够产生T IA s的植物的STR属于STR 2类型.
[Objective] The aims were to obtain cloning of HDR gene from Ginkgo biloba.and study its function.[Method] The coding sequence of HDR gene was cloned from G.biloba by reversed transcription polymerase chain reaction,which was designated as GbHDR （GenBank accession No.：DQ364231）.The cDNA full-length of GbHDR is 1 827 bp containing a 1 425-bp open reading frame （ORF） encoding a 474-amino-acid polypeptide and constructed into the prokaryotic expression vector pTrcGbHDR.The β-carotene biosynthetic pathway in E.coli strain XL1-Blue was reconstructed by transforming with pAC-BETA.This engineered XL1-Blue was transformed with pTrcGbHDR.[Result] A 1 441 bp GbHDR was obtained containing a 1 425-bp ORF encoding a 474-amino-acid residues of protein,the predicted molecular weight was 53.2 kD,and predicted isoelectric point was 5.76.Functional complementation assay indicated that GbHDR could promote theβ-carotene accumulation in engineered XL1-Blue harboring pTrcGbHDR and pAC-BETA,and as a result,the engineered bacteria showed the brightly orange given by β-carotene.This suggested that GbHDR had the typical function of known HDR genes.[Conclusion] A engineered bacteria of E.coli which could highly accumulate β-carotene was obtained,which will provide candidate genes and targets for realizing β-carotene metabolic engineering.
