Toxoplasma gondii expresses two distinct lactate dehydrogenase homologous genes during its life cycle in intermediate hosts
Toxoplasma gondii expresses two distinct lactate dehydrogenase homologous genes during its life cycle in intermediate hosts
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DOI：
10.1016/s0378-1119(96)00566-5
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发表时间：
1997-01-03
期刊：
影响因子：
3.5
通讯作者：
Parmley, SF
中科院分区：
文献类型：
--
作者：
Yang, SM;Parmley, SF
刚地弓形虫的两个基因在寄生虫的生命周期中有差异表达。LDH1和LDH2基因编码的多肽类似于多种生物体内的乳酸脱氢酶（LDH; L-lactate:NAD(+) oxidoreductase, EC 1.1.1.27）。它们在编码区具有64.0%的核苷酸同源性，并且在相同的相对位置上都有一个内含子。LDH1和LDH2的氨基酸序列同源性为71.1%。LDH1和LDH2与恶性疟原虫的LDH最相似（氨基酸同源性分别为46.5%和48.5%）。LDH2 mRNA仅在慢殖子期检测到，而LDH1 mRNA在慢殖子和速殖子期均检测到。然而，通过等电聚焦和免疫印迹分析，在每个阶段只发现一个LDH亚型表达。此外，携带氯霉素乙酰转移酶（chloramphenicol acetyltransferase， CAT）编码序列和LDH2启动子序列的报告基因的表达在碱性培养基（pH 8.2，已知可诱导慢速子特异性抗原的表达）的组织培养中显著上调，而携带LDH1启动子序列的CAT报告构建体的表达在类似处理下下调。这些结果表明，弓形虫体内LDH的表达受发育调控，并提示弓形虫体内的阶段转化与碳水化合物或能量代谢的改变之间可能存在相关性。
Two Toxoplasma gondii genes were characterized that are differentially expressed during the parasite's life cycle. The genes named LDH1 and LDH2, respectively, encode polypeptides similar to the enzyme lactate dehydrogenase (LDH; L-lactate:NAD(+) oxidoreductase, EC 1.1.1.27) from a variety of organisms. They show 64.0% nucleotide identity in the coding region and both have an intron at the same relative position. The deduced amino acid sequences of LDH1 and LDH2 share 71.1% identity. LDH1 and LDH2 are most similar to an LDH of Plasmodium falciparum (46.5% and 48.5% amino acid identities, respectively). The mRNA of LDH2 was only detected in the bradyzoite stage, while the mRNA of LDH1 was detected in both the bradyzoite and tachyzoite stages. However, by isoelectric focusing and immunoblot analysis, only one LDH isoform was found to be expressed in each stage. Furthermore, the expression of a reporter gene carrying chloramphenicol acetyltransferase (CAT) coding sequence and the putative LDH2 promoter sequence was significantly up-regulated by growing parasites in tissue culture in media with alkaline pH (pH 8.2, a condition known to induce the expression of bradyzoite-specific antigens), while the expression of a CAT reporter construct carrying the putative LDH1 promoter sequence was down-regulated by similar treatment. These results indicate that LDH expression is developmentally regulated in T. gondii and suggest a possible correlation between stage conversion and alteration in carbohydrate or energy metabolism in this parasite.