FUNCTION AND ASSEMBLY OF CO2 ASSIMILATORY ENZYMES

健康的细胞活动依赖于适当的组装和 中间代谢的关键酶的后续催化作用。 我们的主要兴趣和长期目标是了解 调节二氧化碳被吸收为有机物质的过程 细胞中的化合物，这是所有有机体共同的过程。 初级二氧化碳同化是由核酮糖酶催化的 1，5-二磷酸(RuBP)羧基酶/加氧酶(Rubisco)。这种蛋白质 也有能力作为内部单加氧酶和 在合适的条件下催化RuBP的氧化裂解。 因此Rubisco是一种双功能蛋白质，其中相同的多肽链 催化细胞内两个相互竞争的反应的第一步 代谢；事实上，最近的研究表明，这种独特的酶可能 具有异构酶、同分异构酶和磷酸酶的功能。这 因此，研究针对三个主要领域：(1)通过什么机制 伴侣蛋白对大(L)和小(S)折叠的影响 L/8S/8Rubisco的亚基；(2)Rubisco的分子基础 能够区分它的两种气体底物二氧化碳 和氧；以及(3)Rubisco活性被 在细胞内通过翻译后修饰和使用 额外的蛋白质。已经为Rubisco建立了一个系统 折叠研究将极大地加强最近的结果，表明 已知的伴侣蛋白以外的因子(S)的重要性。在……里面 此外，还制定了新的遴选程序，以加强 Rubisco底物专一性研究；因此残基和区域 影响催化和底物专一性可以在一定程度上被阐明 超越了有偏见的定点突变程序。这类研究 将很好地增强X射线和结构模型 为几个RuBisCO提供了支持。因此，这些研究呈现了一种极好的 将控制细胞新陈代谢与适当的折叠联系起来的机会 以及一种重要但复杂的寡聚蛋白的功能。

Healthy cellular activity is dependent on the proper assembly and subsequent catalytic function of key enzymes of intermediary metabolism. Our primary interest and long-term goal is to understand factors which regulate the process by which carbon dioxide is assimilated into organic compounds of the cell, a process which is common to all organisms. Primary carbon dioxide assimilation is catalyzed by the enzyme ribulose 1,5-bisphosphate (RuBP) carboxylase/oxygenase (RubisCO). This protein also has the capacity to function as an internal monooxygenase and catalyzes the oxygenolytic cleavage of RuBP under suitable conditions. RubisCO is thus a bifunctional protein in which the same polypeptide chain catalyzes the first step of two competing reactions of cellular metabolism; indeed recent studies indicate that this unique enzyme may function as an isomerase, an epimerase, and a phosphatase as well. This study is thus directed at three major areas: (1) the mechanism by which chaperonin proteins influence the folding of large (L) and small (S) subunits of L/8S/8 RubisCO; (2) the molecular basis by which RubisCO is able to discriminate between its two gaseous substrates, carbon dioxide and oxygen; and (3) the process by which the activity of RubisCO is regulated in the cell via posttranslational modification and the use of additional proteins. A system has been established for the RubisCO folding studies that will greatly enhance recent results indicating the importance of factor(s) other than known chaperonin proteins. In addition, novel selection procedures have been developed to enhance the RubisCO substrate specificity studies; thus residues and regions that influence catalysis and substrate specificity may be elucidated at a level beyond prejudicial site-directed mutagenesis procedures. Such studies will nicely enhance X-ray and structural models that have already been provided for several RubisCOs. These studies thus present an excellent opportunity to relate control of cellular metabolism to the proper folding and function of an important, yet complex oligomeric protein.