Structure Function of Food Related Proteins

我们NSERC资助的研究计划的长期目标是了解解释蛋白质结构如何决定蛋白质功能的基本过程。在食品系统中，蛋白质（包括酶）在质地、风味、气味、营养和食品安全/植物病理学（例如，抗微生物和植物防御蛋白）以及加工助剂（例如，凝乳酶在干酪生产中使牛奶凝结）。该提案的研究重点是一组称为天冬氨酸蛋白酶的酶，它们具有高度相似的结构和作用模式，最好的代表是胃酶胃蛋白酶。尽管有这种一致性，但存在广泛的不同功能，使它们成为研究蛋白质结构如何决定功能的理想模型。在我们小组和其他人以前研究的基础上，拟议的研究计划解决了两个主要领域的基本知识差距：1）植物中天冬氨酸蛋白酶的食品腐败相关生物活性蛋白片段; 2）天冬氨酸蛋白酶结构耐热性和碱性的基础，以及对特定目标的选择性。对于第一个研究领域，与来自非植物来源的天冬氨酸蛋白酶相比，来自植物的天冬氨酸蛋白酶具有额外的部分，称为植物特异性插入物（PSI）。PSI是植物天冬氨酸蛋白酶与膜相互作用的关键，包括作为植物对入侵真菌的免疫反应的一部分的对抗植物病原体的活性。与膜接触的结构和特定点将在分子细节的最高水平上得到解决，以便更好地理解PSI的作用模式。第二个研究领域将涉及解决一个很少研究的疟疾天冬氨酸蛋白酶的结构（血浆蛋白酶V）与众所周知的抑制剂复合以缩小结合位点的可能范围，从而指导计算机辅助设计特异性针对Plasmepsin V抑制剂。其他研究将有助于理解非典型天冬氨酸蛋白酶如何能够在极端温度下工作（来自酸性温泉中的生物体的嗜热蛋白）和非酸性pH（来自人类肾脏的肾素）。嗜热蛋白酶和肾素将作为模板工程胃蛋白酶（这是不是温度或中性pH值稳定），通过提供一种手段，测试关键结构特征的稳定效果。拟议的研究计划的影响将是提高有关AP结构和功能的知识，从而使新的战略干预食品相关的挑战，如植物疾病和酶的生物技术应用。

The long-term goal of our NSERC-funded research program has been to understand the fundamental processes that explain how protein functionality is dictated by protein structure. In food systems, proteins (including enzymes) have prominent roles in texture, flavour, odour, nutrition and prophylaxis in food safety/plant pathology (e.g., antimicrobial and plant defense proteins) as well as being processing aids (e.g., chymosin coagulates milk in cheese production). The research focus of this proposal is on a group of enzymes called aspartic proteases which share highly similar structures and modes of action, that are best represented by the stomach enzyme pepsin. Despite this uniformity, a wide spectrum of different functions exist making them an ideal model to study how protein structure determines function. Building on previous research by our group and others, the proposed research program addresses fundamental knowledge gaps in two overarching areas: 1) food spoilage-related bioactive protein segments of aspartic proteases in plants; and 2) the underpinnings of aspartic protease structure tolerance to heat and alkalinity, and selectivity for particular targets. For the first research area, aspartic proteases from plants have an extra portion compared to those from non-plant sources called the plant-specific insert (PSI). The PSI is critical for plant aspartic proteases to interact with membranes, including activity against plant pathogens as part of plants’ immune responses to invading fungi. The structure and specific points of contact with membranes will be solved at the highest level of molecular detail in order to better understand the mode of action of the PSI. The second research area will entail solving the structures of a little-studied malarial aspartic protease (plasmepsin V) complexed with well-known inhibitors to narrow the possible range of binding sites, so as to direct computer-aided inhibitor design specific to plasmepsin V. Other studies will contribute to understanding how atypical aspartic proteases are able to work at extreme temperature (thermopsin from an organism found in acidic hot springs) and non-acidic pH (renin from human kidney). Thermopsin and renin will serve as templates for engineering pepsin (which is not temperature- or neutral pH-stable) by providing a means of testing the stabilizing effects of key structural features. The impact of the proposed research program will be to improve knowledge regarding AP structures and functions thereby enabling novel strategies for interventions in food-related challenges such as plant diseases and enzyme biotechnological applications.