Exploration of the regulation and structure-function relationships of enzymes and proteins involved in sulfur amino acid metabolism and storage in bacterial and plant systems

蛋白质工程和其他纳米科学在提供新的环境友好技术以解决社会面临的许多挑战方面具有显著的潜力。我的实验室为这项研究所需的跨学科方法做好了准备。我们独特的专业知识跨越蛋白质生物化学，微生物学和植物科学。由此产生的知识转换机会（例如生物化学和植物科学之间的知识转换）和所采用技术的多样性提供了一个强有力的培训环境。我的主要研究方向是氨基酸代谢，同时我们也关注蛋白质的结构-功能关系。这些主题的普遍性为我们在不同系统中的研究提供了基础，正如本提案中描述的两个正在进行的项目所说明的那样：工程吡哆醛5 ' -磷酸酶。蛋白质是大型生物分子，由称为氨基酸的单个构建块组成，以复杂的三维模式折叠。这使得活细胞内数千种不同蛋白质中的每一种都具有独特和特定的功能。蛋白质的众多作用之一是催化化学反应。酶是一种大的生物分子，通常是蛋白质，它催化生化反应，在活细胞的生理条件下将开始的“底物”转化为特定的“产物”。为生物技术量身定制酶的经济前景刺激了对蛋白质工程研究的投资和兴趣。2010年全球工业酶的市场价值为33亿美元，预计这一价值将稳步增长。催化氨基酸转化的酶通常依赖于吡哆醛5 ' -磷酸（PLP）。PLP辅助因子的多功能性使得它可以催化一系列反应。我们将继续我们的研究探索复杂和微妙的结构-功能关系，这些关系是这些酶特异性的基础。我们的长期目标是应用这些知识来修改它们的特异性，以满足工业过程的要求。2. 改变植物的氨基酸平衡以改善其营养特性。鹰嘴豆等谷物豆类提供了全球约10%的膳食蛋白质供应，每年为加拿大带来约27亿美元的出口收入。然而，这些种子缺乏必需的氨基酸蛋氨酸，平均含量比人体营养建议的3-5%低5倍。据报道，修改某一作物收获部分氨基酸含量的尝试可分为“推”或“拉”策略。推法改变了缺乏氨基酸的生物合成途径中代谢物的通量，从而增加了可溶性氨基酸库。互补拉动策略侧重于端点，试图增加种子储存蛋白中目标氨基酸的含量。我们正在努力：(1)在目标植物物种的背景下，深入了解这些生物合成酶的调控，以便更巧妙地增加可溶性蛋氨酸库；(2)建立两相筛选，以便对天然种子储存蛋白进行工程改造，以修改其氨基酸谱。这一策略是新颖的，为科学学科之间的知识转化提供了一个例子。我们的研究将为提高谷物豆科植物的营养品质提供必要的知识基础。我们创新的两相筛选也有潜力应用于其他作物的氨基酸谱工程（例如，增加谷物的赖氨酸含量）。

Protein engineering and other nanoscale sciences possess remarkable potential to provide new environmentally friendly technologies to address a number of the challenges facing society. My lab is well positioned for the transdisciplinary approach required for this research. Our distinct blend of expertise spans protein biochemistry, microbiology and plant science. The resulting opportunities for knowledge translation (e.g. between biochemistry and plant science) and the diversity of techniques employed provide a strong training environment. The primary focus of my research program is amino acid metabolism and we have focused on protein structure-function relationships. The ubiquitous nature of these themes provides the basis for our studies in diverse systems, as illustrated by the two ongoing projects described in this proposal: 1. Engineering pyridoxal 5’-phosphate enzymes. Proteins are large biological molecules, formed of individual building blocks called amino acids, which fold in a complex three-dimensional pattern. This enables the unique and specific function of each of the thousands of distinct proteins inside a living cell. One of the many roles of proteins is in the catalysis of chemical reactions. Enzymes are large biological molecules, generally proteins, which catalyze biochemical reactions, converting the starting `substrate` to a specific `product` under the physiological conditions of the living cell. The economic prospects of tailoring enzymes for biotechnology have spurred investments and interest in protein engineering research. The 2010 global market value of industrial enzymes was $3.3 US billion, a value predicted to grow steadily. Enzymes catalyzing transformations of amino acids are generally dependent on pyridoxal 5’-phosphate (PLP). The versatility of the PLP cofactor is such that it can catalyze an array of reactions. We will continue our research probing the complex and subtle structure-function relationships that underlie specificity in these enzymes. Our long-term goal is the application of this knowledge to modify their specificity to meet the requirements of industrial processes. 2. Modifying the amino acid balance of plants to improve their nutritional properties. Grain legumes, such as chickpea, provide approximately 10% of the world supply of dietary protein and produce approximately $2.7 billion (CDN) in export revenue for Canada, annually. However, the seeds are deficient in the essential amino acid methionine, containing on average 5-fold less than the recommended 3-5% recommended for human nutrition. Reported attempts to modify the amino acid content of the harvested portion of a given crop plant can be classified as either ‘push’ or ‘pull’ strategies. Push approaches alter the flux of metabolites in the biosynthetic pathway of the deficient amino acid, thereby yielding an increase in the soluble amino acid pool. The complementary pull strategy focuses on the endpoint, attempting to increase the content of the target amino acid in the storage proteins of the seed. We are working to: (1) develop a thorough understanding of the regulation of these biosynthetic enzymes, in the context of the target plant species, in order to more subtly increase the soluble methionine pool and (2) establish a two-phase screen to enable engineering of the native seed storage proteins to modify their amino acid profile. This strategy is novel and provides an example of knowledge translation between scientific disciplines. Our research will provide the knowledge base required to improve the nutritional quality of grain legumes. Our innovative two-phase screen also has the potential to be applied to engineer the amino acid profiles of other crops (e.g. increasing the lysine content of cereals).