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RUI: Structure, function and evolutionary history of beta-amylase2 (BAM2) in plants

RUI：植物中β-淀粉酶2（BAM2）的结构、功能和进化史

基本信息

批准号：
1932755
负责人：
Jonathan Monroe
金额：
$ 42.54万
依托单位：
James Madison University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-03-01 至 2024-02-29
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1932755&HistoricalAwards=false
关键词：
RUI Structure function evolutionary history

项目摘要

Starch is an important carbon- and energy-storage compound in plants and it has widespread use in industry and as part of the human diet. With this project the researchers aim to better understand the structure and function of a plant enzyme that they suspect plays and unusual role in starch metabolism. Potential long-term benefits of the research include modified crops that contain starch with properties suitable for improved food and industrial applications. In some plants this enzyme is encoded by a complex gene, the understanding of which could shed light on how genes evolve. The research will be carried out at a predominantly undergraduate institution and involve at least 12 undergraduates helping prepare them for graduate school and careers in science. The students will be involved in all aspects of the work. In addition, the project will support a postdoctoral scholar that will obtain valuable teaching experience in lectures and laboratories of introductory and advanced courses, as well as bringing valuable intellectual and technical assets to the lab. Most importantly, they will be able to develop undergraduate research mentoring skills and acquire practical advice for building a successful career at a predominantly undergraduate institution.Starch is a complex polymer of glucose composed mostly of amylopectin, a highly branched molecule with layers of short chains that are 12-15 glucose units long. In green leaves starch accumulates during the day and is broken down at night so that the leaf can continue to export energy to the entire plant even when photosynthesis is not active. One of the key enzymes known to play an important role in starch degradation is beta-amylase, which hydrolyzes the disaccharide maltose from the ends of amylopectin. The researchers recently discovered that one of the beta-amylases in Arabidopsis called BAM2 is unlike all of the other characterized BAMs in that it is a tetramer, requires K+ for activity, possesses a secondary starch-binding site, and has sigmoidal kinetics. Based on these properties the researchers developed a hypothesis that BAM2 plays a role in starch synthesis as a trimming enzyme to ensure that the short amylopectin chains are of the proper length. To test this hypothesis, they will investigate the catalytic and starch-binding properties of the wildtype and mutant enzymes in detail. In addition, the function of the enzyme will be tested by characterizing the structure of starch isolated from wildtype and mutant plants lacking BAM2. The researchers will also investigate the localization and properties of the BAM2-like protein in rice plants that appears to be part of a longer BAM7 gene with two putative transcriptional start sites. Understanding the role of BAM2 in starch metabolism could have a significant impact on biotechnological efforts to enhance starch yield in crops. The experiments described here may shed light on how starch binding to an allosteric surface of BAM2 influences its catalytic activity. The work may also reveal how novel genes can be generated by fusion events and how they can evolve through duplication and neofunctionalization.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

淀粉是植物中一种重要的碳和能量储存化合物，在工业和人类饮食中有着广泛的应用。通过这个项目，研究人员的目标是更好地了解他们怀疑在淀粉代谢中起作用的植物酶的结构和功能。这项研究的潜在长期效益包括含有淀粉的改性作物，这些淀粉具有适合改善食品和工业应用的特性。在某些植物中，这种酶是由一个复杂的基因编码的，对它的理解可以揭示基因是如何进化的。这项研究将在一个以本科为主的机构进行，至少有12名本科生参与，帮助他们为研究生院和科学职业做好准备。学生将参与工作的各个方面。此外，该项目将支持一名博士后学者，他将在入门和高级课程的讲座和实验室中获得宝贵的教学经验，并为实验室带来宝贵的知识和技术资产。最重要的是，他们将能够培养本科生研究指导技能，并获得实用的建议，以便在以本科为主的机构中建立成功的职业生涯。淀粉是一种复杂的葡萄糖聚合物，主要由支链淀粉组成，支链淀粉是一种高度支化的分子，具有12-15个葡萄糖单元长的短链层。在绿色叶子中，淀粉在白天积累，在晚上分解，这样即使光合作用不活跃，叶子也可以继续向整个植物输出能量。已知在淀粉降解中起重要作用的关键酶之一是β-淀粉酶，其从支链淀粉的末端水解二糖麦芽糖。研究人员最近发现，拟南芥中一种称为BAM 2的β-淀粉酶与所有其他特征BAM不同，因为它是一种四聚体，需要K+才能活性，具有二级淀粉结合位点，并具有S形动力学。基于这些特性，研究人员提出了一个假设，即BAM 2在淀粉合成中起着修剪酶的作用，以确保短支链淀粉链具有适当的长度。为了验证这一假设，他们将详细研究野生型和突变型酶的催化和淀粉结合特性。此外，将通过表征从缺乏BAM 2的野生型和突变体植物中分离的淀粉的结构来测试酶的功能。研究人员还将研究水稻植物中BAM 2样蛋白的定位和特性，该蛋白似乎是具有两个假定转录起始位点的较长BAM 7基因的一部分。了解BAM 2在淀粉代谢中的作用可能对提高作物淀粉产量的生物技术工作产生重大影响。这里描述的实验可能揭示淀粉结合到BAM 2的变构表面如何影响其催化活性。这项工作还可能揭示新基因如何通过融合事件产生，以及它们如何通过复制和新功能化进化。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。