Isolation and characterization of a NADP-dependent glutamate dehydrogenase gene from the primitive eucaryote Giardia lamblia.
Isolation and characterization of a NADP-dependent glutamate dehydrogenase gene from the primitive eucaryote Giardia lamblia.
复制标题
从原始真核生物蓝氏贾第鞭毛虫中分离和鉴定 NADP 依赖性谷氨酸脱氢酶基因。
DOI：
10.1016/s0021-9258(18)42550-1
复制
发表时间：
1992
期刊：
影响因子：
--
通讯作者：
P. Dennis
中科院分区：
文献类型：
--
作者：
J. Yee;P. Dennis
蓝氏贾第鞭毛虫被认为是最早的分支衍生物从真核谱系。基因组和cDNA克隆编码贾第虫NADP依赖性谷氨酸脱氢酶已被分离和表征。使用基因组DNA的Southern杂交表明，编码这种活性的基因是独特的和单拷贝的。引物延伸，S1核酸酶保护，基因组和cDNA序列分析表明，基因转录本内的一个保守的富含AT的序列元件开始之前的ATG翻译起始密码子和短的5'非翻译区不延伸的反式剪接。开放阅读框长1350个核苷酸，编码449个氨基酸的蛋白质。阅读框不被内含子中断，并且初级转录物可能不经历RNA编辑。在贾第鞭毛虫的严格厌氧代谢中，依赖于NADP的谷氨酸脱氢酶活性沿着丙氨酸氨基转移酶参与还原当量（NADPH）通过丙酮酸转化为丙氨酸的循环耗散。贾第虫蛋白的推导的氨基酸序列表现出大量的真菌和真细菌NADP依赖性谷氨酸脱氢酶的同源性。比对缺口位置和氨基酸同一性的比较表明，贾第虫序列与真细菌序列至少与真菌序列一样相似或更相似。这支持了贾第鞭毛虫很早就从真核生物谱系中分化出来的假设。
Giardia lamblia is believed to be the earliest branching derivative from the eucaryotic lineage. Genomic and cDNA clones encoding the giardia NADP-dependent glutamate dehydrogenase have been isolated and characterized. Southern hydridization using genomic DNA indicates that the gene encoding this activity is unique and single copy. Primer extension, S1 nuclease protection, and genomic and cDNA sequence analysis demonstrate that gene transcripts are initiated within a conserved AT-rich sequence element immediately preceding the ATG translation initiation codon and the short 5' untranslated region is not extended by transsplicing. The open reading frame is 1350 nucleotides in length and encodes a protein of 449 amino acids. The reading frame is not interrupted by introns and the primary transcript is probably not subjected to RNA editing. In the strictly anaerobic metabolism of giardia, NADP-dependent glutamate dehydrogenase activity participates along with alanine aminotransferase, in the cyclic dissipation of reducing equivalents (NADPH) through the conversion of pyruvate to alanine. The deduced amino acid sequence of the giardia protein exhibits substantial homology to numerous fungal and eubacterial NADP-dependent glutamate dehydrogenases. Comparisons of alignment gap positions and amino acid identities indicate that the giardia sequence is at least as similar or more similar to the eubacterial sequence than it is to the fungal sequence. This supports the hypothesis that giardia diverged very early from the eucaryotic lineage.