Metabolic Compartmentation of Vertebrate Glutamine Synthetase

脊椎动物谷氨酰胺合成酶的代谢区室

• 批准号: 8718042
• 负责人: James Campbell
• 金额: --
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-04-01 至 1993-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8718042&HistoricalAwards=false
• 关键词: Metabolic; Compartmentation; Vertebrate; Glutamine; Synthetase

The overall goal of this project is an elucidation of the possible molecular events that led to the mitchondrial compartmentation of glutamine synthetase in liver tissue during vertebrate evolution. This localization of the enzyme allowed for the development of uricoteley as a major kind of excretory nitrogen metabolism. Most mitochondrial proteins are coded for in the nucleus, translated in cytosol, and targeted to mitochondria by N-terminal signal sequences. The larger size of the pre-enzyme allows it to be distinguished from the mature enzyme. We have shown this to probably be true for elasmobranch liver mitochondrial glutamine synthetase and we now intend to characterize the import of the pre-enzyme by elasmobranch liver mitochondria in vivo and in vitro. We have also found that in birds and alligators there is no detectable size difference between the nascent and mature glutamine synthetase peptide in liver, despite its mitochondrial matrix localization in tissue. In order to determine if there is an internal targeting sequence in the avian enzyme, we will clone and sequence glutamine synthetase mRNA cDNA from both liver and brain. The enzyme remains in the cytosol in the latter tissue so a comparison of the deduced amino acid sequences for the two should give some clue as to the nature and location of the signal sequence used for import of the liver enzyme. We also will obtain the deduced sequences for elasmobranch and possibly tortoise pre-glutamine synthetase for comparative purposes. This comparison should give some indication of the possible changes that have occured during evolution that led from a classical presequence mechanism for targeting of the enzyme to liver mitochondria in primitive vertebrates to whatever the mechanism used in higher uricotelic vertebrates. This research on the molecular mechanisms of how enzymes are targeted to specific cell compartments is significant to cell biology and biochemistry. The regulation of enzyme activity is a key question for understanding metabolism.//

该项目的总体目标是阐明脊椎动物进化过程中导致肝组织中谷氨酰胺合成酶线粒体区隔的可能分子事件。 该酶的这种定位使得尿科特利发展成为一种主要的排泄性氮代谢。 大多数线粒体蛋白在细胞核中编码，在细胞质中翻译，并通过 N 端信号序列靶向线粒体。 前酶的较大尺寸使其能够与成熟酶区分开来。 我们已经证明这对于软骨鱼类肝脏线粒体谷氨酰胺合成酶来说可能是正确的，现在我们打算在体内和体外表征软骨鱼类肝脏线粒体对前酶的输入。 我们还发现，在鸟类和鳄鱼中，肝脏中的新生和成熟谷氨酰胺合成酶肽之间没有可检测到的大小差异，尽管其线粒体基质定位在组织中。 为了确定禽类酶中是否存在内部靶向序列，我们将从肝脏和大脑中克隆谷氨酰胺合成酶 mRNA cDNA 并进行测序。 该酶保留在后一种组织的细胞质中，因此对两者推导的氨基酸序列进行比较应该可以提供一些关于用于输入肝酶的信号序列的性质和位置的线索。 我们还将获得软骨鱼和可能的陆龟前谷氨酰胺合成酶的推导序列，以用于比较目的。 这种比较应该给出一些关于进化过程中可能发生的变化的指示，这些变化导致从原始脊椎动物中酶靶向肝线粒体的经典前序机制到高等排尿酸脊椎动物中使用的任何机制。 这项关于酶如何靶向特定细胞区室的分子机制的研究对于细胞生物学和生物化学具有重要意义。 酶活性的调节是理解新陈代谢的关键问题。//