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本文测定了浑球红细菌Ｒｈｏｄｏｂａｃｔｅｒｓｐｈａｅｒｏｉｄｅｓ谷氨酸合酶小亚单位基因（ｇｌｔＤ）及其５＇端和３＇端的序列，全长为２３８７ｂｐ。序列分析表明Ｒ．ｓｐｈａｅｒｏｉｄｅｓｇｌｔＤ基因全长为１２４２ｂｐ。从核苷酸序列推测其蛋白质分子量约为４４ｋＤ。Ｒ．ｓｐｈａｅｒｏｉｄｅｓｇｌｔＤ基因与Ａｚｏｓｐｉｒｉｌｕｍｂｒａｓｉｌｅｎｓｅ和Ｅｓｃｈｅｒｉｃｈｉａｃｏｌｉ的ｇｌｔＤ基因ＤＮＡ序列有很高的同源性。其蛋白质氨基酸序列与Ａ．ｂｒａｓｉｌｅｎｓｅ谷氨酸合酶小亚基蛋白ＧｌｔＤ也具有很高的同源性。对Ｒ．ｓｐｈａｅｒｏｉｄｅｓ谷氨酸合酶小亚基蛋白ＧｌｔＤ功能区的分析表明它们具有很高的保守性。此外，本文还克隆了ｇｌｔＤ的启动子区，构建了ｇｌｔＤ－ｌａｃＺ转录融合子，对其在不同培养条件下的表达进行了分析，结果表明ｇｌｔＤ基因的表达受到１５ｍｍｏｌ／Ｌ亮氨酸的阻遏。而其表达不受同等浓度的谷氨酸、丙氨酸和谷氨酰胺的阻遏。同时，ｇｌｔＤ－ｌａｃＺ在Ｒ．ｓｐｈａｅｒｏｉｄｅｓ野生型以及ｇｌｔＤ和ｇｌｔＢ突变株中的β－半乳糖苷酶活性差异不大，说明ｇｌｔＤ基因不存在自身调控。
In this paper, we determined the sequence of gltD and its 5 ’and 3’ end of Rhodobacterphaeroides glutamic acid synthase small subunit gene (total length is 2387 bp). Sequence analysis showed R. The sphaeroidesgltD gene is 1242bp in length. From the nucleotide sequence deduced that the molecular weight of its protein is about 44kD. R. The sphaeroidesgltD gene has high homology with the gltD gene DNA sequences of Azospirilumbrasilense and Escherichia coli. Its protein amino acid sequence and A. brasilense glutamate synthase small subunit protein GltD also has a high homology. Right R. Analysis of the gltD functional domains of sphaeroides glutamate synthase small subunit protein showed that they are highly conserved. In addition, gltD promoter region was cloned and the gltD-lacZ transcriptional fusion was constructed. The expression of gltD gene under different culture conditions was analyzed. The results showed that gltD gene expression was inhibited by 15 mmol / L leucine. While its expression is not repressed by glutamate, alanine and glutamine at the same concentrations. Meanwhile, gltD-lacZ is in R. There was no significant difference in β-galactosidase activity between wild-type sphaeroides and gltD and gltB mutant strains, indicating that there is no self-regulation of gltD gene.