摘要
在鼠伤寒沙门氏菌中，由嘌呤从头合成途径合成ＩＭＰ经１０步酶促反应，涉及１０个结构基因，其中ｐｕｒＪｐｕｒＨ和ｐｕｒＤ构成１个操纵子，除ｐｕｒＢ外均受反式调节基因ｐｕｒＲ的负调控。本文以ｐｘｒＪＨＤＯ~＋和Ｏ~Ｃ突变体为材料，通过体内克隆法分别克隆到Ｏ~＋ｐｕｒＪＨＤ（ｐ２－９）和Ｏ~ＣｐｕｒＪＨＤ（ｐＣ－１２）操纵子；遗传互补和限制性内切酶分析作出了ｐ２－９和ｐＣ－２的物理图谱。经２次亚克隆分别获得可直接测定调控区序列的重组质粒ｐＬＫ２１２（Ｏ~＋）和ｐＣ－２６（Ｏ~Ｃ）。序列测定表明，鼠伤寒沙门氏菌ｐｕｒＪＨＤ的顺式元件中亦存在１６ｂｐ保守序列（以下简称ＰＵＲｂｏｘ），其序列为ＧＣＧＣＡＡＡＣＧＴＴＴＴＣＧＴ。Ｏ~Ｃ突变产生于ＰＵＲｂｏｘ第１４位碱基突变（由Ｃ→Ｔ）。这一结果从ＰＵＲｂｏｘ功能上为阐明嘌呤基因协同表达调控机理提供了新的证据。
It has been known that 10 enzymatic reactions are involved in de novo biosynthesis of IMP in Salmonella typhimurium. 10 genes encoding the enzymes have beenlocalized on the Salmonella typhimurium chromosome. Seven structure genes including pur JHD operon are negatively regulated by purR.In this study the purJHDoperon containing O￣+ and O￣c were cloned in vivo respectively. Two preliminary clones, p2-9(O￣+) and pC-12 (O￣c) were identified to be the hybrid plasmids carrying intact pur JHD operon by genetic complementary test and reconstruction enzyme analysis. The fragments of O￣+ and O￣c were subcloned on to pUC19 and DNAsequence were determined directly by DNA sequencer. The DNA sequence of O￣+ fragment revealed that a 16 base consensus sequence (named PUR box) GCGCAAACGTTTTCGT also existed in control region of pur JHD operon in Salmonella typhimurium. The DNA sequence of O￣c fragment indicated that only one base changeoccured at the 14th position of PUR box(C→T). Our result strongly support theidea that PUR box is binding region of purR protein. Recieved Dec ember 3,1993. This project supported by National Nature Science Foundation of China and '8.5' Major Project Fund of Chinese Academia
基金
国家自然科学基金
中国科学院"8.5"重点课题
