REGULATION OF LIPID METABOLISM IN E COLI

大肠杆菌脂质代谢的调节

基本信息

批准号：
3285596
负责人：
Charles O Rock
金额：
$ 29.47万
依托单位：
ST. JUDE CHILDREN'S RESEARCH HOSPITAL
依托单位国家：
美国
项目类别：
财政年份：
1984
资助国家：
美国
起止时间：
1984-12-01 至 1996-11-30
项目状态：
已结题

项目摘要

Fatty acid and phospholipid synthesis is a vital facet of bacterial physiology that is tightly regulated at several levels. Phospholipids comprise approximately 15% of the dry weight of a bacterial cell and the advantage of maintaining fine control over their biosynthesis is evident from the importance of phospholipid composition in membrane structure and function. Our experimental plan proposes to investigate the regulation of bacterial lipid metabolism at three key points. The first control point is at the initiation of fatty acid biosynthesis. The evidence indicates that an early step in the fatty acid biosynthetic pathway is rate-limiting. The initiation of fatty acid synthesis is more complicated, potentially utilizing three distinct mechanisms. The two key enzymes are beta-ketoacyl-ACP synthase III and acetyl-CoA:ACP transacylase. We have cloned and characterized the synthase III (fabH) gene providing the necessary tools to critically test the role of this enzyme in initiation. Virtually nothing is known about the genetics or biochemistry of acetyl transacylase and a major effort to acquire the molecular reagents to establish the role of acetyl transacylase in fatty acid initiation is the next important step. Control mechanisms that regulate fatty acid composition are located at later points in the fatty acid biosynthetic pathway. Unsaturated fatty acids (UFA) are critical components that are essential for cell survival and modulate the activity of membrane enzymes and transport systems. The sophisticated regulation of UFA synthesis has been extensively investigated and is known to involve two genes of fatty acid biosynthesis (fabA and fabB) and the transcriptional regulator, fadR. We have identified and cloned a fourth gene, designated fabJ, that is required for UFA biosynthesis. Characterizing the structure and function of the fabJ gene product is essential to understanding the mechanisms that govern UFA production. A third level of control is exerted by 2-acyl-GPE acyltransferase/acyl- ACP synthetase, an acyltransferase that maintains membrane phospholipid structure by recycling lysophospholipids that are generated as a byproduct in the synthesis of other molecules or by the action of phospholipases. This enzyme is also thought to be responsible for the uptake and incorporation of exogenous fatty acids and lysophospholipids into the membrane. We have isolated mutants and cloned the structural gene (aas) for this enzyme thus providing the molecular tools needed to define the structure and function of this membrane-associated acyltransferase.

脂肪酸和磷脂合成是细菌的重要方面生理学受到多个层次的严格调节。磷脂约占细菌细胞干重的15％和保持对其生物合成的良好控制的优势是明显的从磷脂组成在膜结构和功能。我们的实验计划建议调查调节细菌脂质代谢在三个关键点。第一个控件点是脂肪酸生物合成的开始。证据表明脂肪酸生物合成途径的早期步骤是限制速率。脂肪酸合成的开始更多复杂的，可能利用三种不同的机制。两个关键酶是β-Ketoacyl-ACP合酶III和乙酰-COA：ACP 透射地板。我们已经克隆并表征了合成酶III（FABH）基因提供了必要的工具来批判性测试这一角色酶的酶。几乎没有关于遗传学或乙酰基透镜的生物化学和获得的重大努力分子试剂以确定乙酰基透镜在脂肪中的作用酸的开始是下一个重要步骤。控制机制调节脂肪酸成分位于脂肪的较晚点酸生物合成途径。不饱和脂肪酸（UFA）很关键对于细胞存活至关重要的组件并调节活性膜酶和运输系统。复杂的法规 UFA合成已得到广泛研究，已知涉及两个脂肪酸生物合成基因（FABA和FABB），以及转录调节器Fadr。我们已经确定并克隆了第四 UFA生物合成所需的基因，指定为FABJ。表征FabJ基因产物的结构和功能是了解控制UFA生产的机制至关重要。 2-acyl-GPE酰基转移酶/酰基 - ACP合成酶，一种维持膜磷脂的酰基转移酶通过回收作为A的溶血磷脂的结构合成其他分子或通过作用的副产品磷脂酶。该酶也被认为是摄取和掺入外源脂肪酸和溶血磷脂进入膜。我们已经孤立的突变体并克隆了结构该酶的基因（AAS）因此提供了所需的分子工具定义该膜相关的结构和功能酰基转移酶。