肌苷和鸟苷生产菌中嘌呤核苷合成途径三段基因序列的分析

为了研究肌苷和鸟苷生产菌中与产苷有关的嘌呤核苷合成途径的遗传背景，选择了pur操纵子的启动子序列、编码SAMP合成酶的purA基因和编码GMP合成酶的guaA基因，设计合适的引物，分别从野生菌、一株肌苷低产菌和肌苷鸟苷高产菌中扩增出相应片段，经克隆和测序后，对它们进行比较和分析。分析结果表明两株生产菌的purA基因发生了1个碱基缺失，导致阅读框发生移码突变；而鸟苷高产菌在pur操纵子的启动子部分和操纵子抑制蛋白结合区域发生了近10％的突变，可能影响整个操纵子的表达调控。

Analysis of Three Nucleotide Sequences Involved in the Purine Nucleotides Biosynthesis in Inosine and Guanosine-producing Bacilus subtilis

In order to study the genetic background involved in the purine nucleotides biosynthesis in the inosine and guanosine producing Bacilus subtilis, the promoter domain of the pur operon, purA gene encoding SAMP synthetase, and guaA gene encoding GMP synthetase, were amplified by PCR from a wild type strain, a low yield inosine producing strain, a inosine producing strain and a guanosine producing strain. After cloning and sequencing of PCR products, the nucleotide sequences from four strains were aligned with the reported corresponding sequences. A one base deletion is discovered in purA gene from inosine producing strain and guanosine producing strain, which will cause the open reading frame shift mutation. And nearly 10% base mutations in the entire and pur operon repressor binding domain of pur operon are observed in guanosine producing strain, which may affect the expression regulation mode of the entire operon.