Regulation of Assimilatory Nitrate Reductase

Solomonson 9317557硝酸盐同化途径是无机氮转化为生物有用的有机形式的主要途径。在硝酸还原酶(NR)的催化下，调节这一途径的第一步对于防止中间体(亚硝酸盐和氨)的有毒积累、确保硝酸盐的有效利用以及允许快速适应环境条件的变化是重要的。以往的研究结果表明，NR受多种效应因子和环境因素在多个不同水平上的调节，反映了该酶的关键作用和途径调控的生物学意义。我们的研究将集中于在分子(酶)水平上阐明对NR的调控至关重要的分子决定因素和机制，并建立各种调控模式之间的相互关系。具体目标包括：a)确定参与NR周转、催化、结合或调节的官能团，以及这些基团相对于酶上的功能结构域或主要序列位置的定位；以及b)确定可能的活性调节剂，如蛋白激酶/磷酸酶、金属结合效应物(例如，一氧化氮或氰化物)或其他效应物对NR周转和催化效率的影响。我们研究的最终目标是从这项研究和其他研究中获得信息，以制定程序来提高天然氮的催化效率，并调节其作用，以努力提高农业生产力。%硝酸盐是生物体内有机氮的主要来源。硝酸盐转化为生物有用的有机形式的过程称为硝酸盐同化，存在于包括细菌、酵母、真菌和高等植物在内的各种生物体中，这些生物体反过来为包括人类在内的其他形式的生命提供营养氮需求。这项研究的目标之一是开发提高硝酸盐同化途径中的关键酶--硝酸还原酶(NR)的催化效率和活性的策略。我们目前研究计划的重点是确定NR分子的官能团和其他有助于我们了解蛋白质的因素。然后，我们可以利用这些信息来设计出农业上有趣的植物，使其具有更有效的氮代谢和更高的生产能力。氮代谢改善的植物将减少向作物供应化肥的需求。***

Solomonson 9317557 The nitrate assimilatory pathway is the major route by which inorganic nitrogen is converted to a biologically useful organic form. Regulation of the first step in this pathway, catalyzed by nitrate reductase (NR), is important to prevent toxic accumulation of intermediates (nitrite and ammonia), to assure efficient utilization of nitrate, and to permit rapid adaptation to changes in environmental conditions. Results of previous studies have indicated that NR is regulated at several different levels by multiple effectors and environmental factors reflecting the key role of this enzyme and the biological importance of pathway regulation. Our research will focus on elucidating molecular determinants and mechanisms which are important for the regulation of NR at the molecular (enzyme) level and establishing interrelationships between various modes of regulation. Specific aims will include: a) identification of functional groups involved in NR turnover, catalysis, binding or regulation, and the localization of these groups with respect to functional domain or primary sequence site on the enzyme; and b) determination of effects of possible activity modulators such as protein kinases/phosphatases, metal binding effectors (e.g., nitric oxide or cyanide), or other effectors on NR turnover and catalytic efficiency. The ultimate goal of our research is to obtain information from this and other studies to develop procedures for increasing the catalytic efficiency of NR and for regulating its action in an effort to increase agricultural productivity. %%% Nitrate is the major source of organic nitrogen in biological organisms. The process by which nitrate is converted to a biologically useful, organic form, termed nitrate assimilation, occurs in a wide variety of organisms including bacteria, yeast, fungi and higher plants, which in turn supply the nutritional nitrogen requirements for other forms of life, including human. One of the goals of this r esearch is to develop strategies for increasing the catalytic efficiency and for regulating the activity of the key enzyme, nitrate reductase (NR), in the nitrate assimilation pathway. The focus of our current research program is to identify the functional groups of the NR molecule and other factors that will help us learn more about the protein. We may then use this information to engineer agriculturally interesting plants with more efficient nitrogen metabolism and increased production capacity. Plants with improved nitrogen metabolism will result in decreased need to supply chemical fertilizers to our crops. ***