Metabolic Organization in Neurospora

本项目将对粗神经孢子虫精氨酸生物合成反馈敏感酶的结构、组装及其相互关系进行研究。前七种生物合成酶，包括反馈敏感酶、乙酰谷氨酸合成酶和乙酰谷氨酸激酶，都定位于线粒体。这些酶是未连接的精氨酸-14和精氨酸-6基因的产物。后者编码乙酰谷氨酸激酶和乙酰谷氨酰磷酸还原酶的多蛋白前体；前体在进入线粒体时被分裂成可分离的蛋白质。将进行分子分析，以研究乙酰谷氨酸激酶和乙酰谷氨酰磷酸还原酶的多蛋白前体的生物学作用和进化起源。测定乙酰谷氨酸合成酶的结构和催化性能。研究乙酰谷氨酸合成酶、乙酰谷氨酸激酶和乙酰谷氨酰磷酸还原酶之间的结构和功能关系，以评估反馈抑制、酶合成和组装的各种协调模型。将进行遗传和生化分析，以确定乙酰谷氨酸激酶在乙酰谷氨酸合成酶的合成、加工、组装和功能中的作用。表型与精氨酸从细胞质转运到线粒体基质的缺陷一致的突变体将被分离和表征。这些结果将对理解真核细胞中的代谢调节和线粒体（和其他细胞器）的组装具有重要意义。像人这样的复杂生物的细胞与像细菌这样的低等生物的细胞是有区别的，因为它们具有合成和分解普通生物分子的机制。为了防止这些潜在的竞争过程同时发生，它们通常被细胞膜隔开，其中一个过程被限制在膜封闭的细胞器中。这些差异需要在细胞膜内移动分子的机制和利用新的机制来控制代谢。细胞内定位缺陷会对生物体的生存造成严重后果。该项目将描述用于控制氨基酸精氨酸合成的机制，以及精氨酸跨细胞膜运输的重要性，作为理解复杂细胞和生物体独特调节机制特征的第一步。＊＊＊

9604620 Weiss This research project will characterize the structure, assembly and inter-relationships of the feedback sensitive enzymes of arginine biosynthesis in Neurospora crassa. The first seven biosynthetic enzymes, including the feedback-sensitive enzymes, acetylglutamate synthase and acetylglutamate kinase, are localized in the mitochondria. These enzymes are products of the unlinked arg-14 and arg-6 genes. The latter encodes a polyprotein precursor of acetylglutamate kinase and acetylglutamyl-phosphate reductase; the precursor is cleaved into separable proteins upon entry into the mitochondrion. A molecular analysis will be performed to investigate the biological role and evolutionary origin of the polyprotein precursor of acetylglutamate kinase and acetylglutamylphosphate reductase. The structural and catalytic properties of acetylglutamate synthase will be determined. The structural and functional relationships between acetylglutamate synthase, acetylglutamate kinase and acetylglutamyl-phosphate reductase will be investigated to evaluate various models for coordination of feedback inhibition, enzyme synthesis and assembly. Genetic and biochemical analyses will be performed to ascertain the role(s) of acetylglutamate kinase in synthesis, processing, assembly and functioning of acetylglutamate synthase. Mutants with a phenotype consistent with defects in arginine transport from the cytosol to the mitochondrial matrix will be isolated and characterized. The results will be of significance in understanding metabolic regulation and the assembly of mitochondria (and other organelles) in eukaryotic cells. %%% The cells of complex organisms such as man are distinguishable from lower organisms such as bacteria by the presence of machinery for both the synthesis and breakdown of common biological molecules. In order to prevent the simultaneous occurrence of these potentially competing processes, they are often separated by intracellular membranes, with one of the processes confined to a mem brane-enclosed organelle. These differences require mechanisms to move molecules across intracellular membranes and the utilization of novel mechanisms to contol metabolism. Defects in intracellular localization can have serious consequences for the survival of the organism. This project will characterize the mechanism used to control the synthesis of the amino acid arginine and the importance of transport of arginine across an intracellular membrane as a first step in understanding the unique regulatory mechanisms characteristic of complex cells and organisms. ***