巴西固氮螺菌Yu62glnZ基因及其相邻基因的克隆和序列分析

通过原位杂交从巴西固氮螺菌（Azospirillum brasilense)Yu62的基因组文库中获得glnZ基因的阳性克隆，对该阳性克隆进行亚克隆和序列分析，结果表明glnZ基因位于3.7kb的SaLI片段上，glnZ基因编码区长336bp，编码的产物是Pz蛋白，由112个氨基酸组成，分子量为1.12kD。用Blastax软件对Pz蛋白的氨基酸序列在GenBank数据库中进行同源比较，结果表明Pz蛋白与其它几种固氮菌及大肠杆菌的GlnK蛋白的同源性（identities）达66％以上；与PⅡ蛋白的同源性达64％以上。glnZ基因上游是部分ubiH-like基因，与E.coli ubjH基因（编码辅酶Q，ubiquinone)N－端有31％的同源性（identity）和50％相似性（similarity)；glnZ基因下游是aat-like基因，与E.coli和Bacillus subtilis aat基因（编码天冬氨酸氨基转移酶，aspartate aminotransferase)有同源性和相似性都为26％和42％；aat-like基因下游是部分ftsK-like基因，与E.coli ftsK基因（编码肽聚糖，peptidoglycan)N-端有42％同源性和56％相似性，这几个基因在GenBank中的登录呈是AF279917。

Cloning and Sequencing of glnZ and the other Genes Clustered Around glnZ from Azospirillum brasilense Yu62

The glnZ gene of A.brasilense was determined in a 3.7 kb SalI fragment,and ubiH-like,aat-like and ftsK-like genes were clustered around glnZ.A partial ubiH-like gene(required for ubiquinone synthesis)precedes glnZ and is transcribed from the opposite strand.The ubiH-likegene of A.brasilense has 31% identitiy and 50% similarity with ubiH gene of E.coli.The aat(aspartate aminotransferase)-like and ftsK(involved in peptidoglycan synthesis during cell septation )-like genes were found clustered downstream of glnZ.The aat-like gene of A.brasilense has 26% identity and 42% similarity with aat gene of E.coli. The ftsK-like gene of A.brasilense has 42% identity and 56% similarity with ftsKgene of E.coli.The glnZ gene encodes 112 amino acid-long Pz polypeptide, maping between positions 1057～1395bp.The amino acid sequence of Pz from A.brasilense is more than 66% identical to that of GlnK proteinfrom several dizotrophs and E.coli.