巴西固氮螺菌Yu62 glnB基因和glnZ基因的克隆和序列分析

Cloning and Sequencing of gln B and gln Z Genes from Azospirillum brasilense

gln B基因编码的 PII蛋白在巴西固氮螺菌的固氮过程中起着非常重要的调控作用 ,而 gln Z是与gln B高度同源的基因 ,其产物 Pz可能也在固氮调控中起作用。本研究用 PCR法克隆了巴西固氮螺菌 Yu6 2gln B基因和 gln Z基因。 DNA序列分析表明 gln B和 gln Z这 2个基因的编码区的长度都为 336 bp,编码 112个氨基酸。将巴西固氮螺菌 Yu6 2菌株与标准菌株 Sp7的 gln B基因和 gln Z基因分别进行比较 ,结果表明这 2个菌株的 gln B基因在编码区的核苷酸顺序完全相同 ,而 gln Z基因在长 336 bp的编码区内有 4个碱基发生变化 ,但改变后都是同义密码子 ,即编码的氨基酸并未改变。 gln B基因和 gln Z基因在核苷酸顺序上的同源性高达 73.2 % ,氨基酸顺序的同源性达 6 6 .7%

The gln B and gln Z genes of Azospirillum brasilense Yu62 are cloned by PCR amplification . DNA analysis shows that the nucleotide sequence of the coding region of gln B gene from A.brasillense Yu62 is same with that of standard A.brasillense Sp7, while the nucleotide sequence of the coding region of gln Z gene from A.brasillense Yu62 is 98.8% identical to that of standard A.brasillense Sp7. There are 4 nucleotide bases that are changed in the coding region of gln Z gene, but the preticted amino acid residues are not changed. The homology of the nucleotide sequences of gln B and gln Z is 73.2%, while the homology of the amino acid sequences encoded by gln Z and gln B is 66.7%.