FUNCTION AND ASSEMBLY OF CO2 ASSIMILATORY ENZYMES

健康的细胞活动依赖于适当的组装， 中间代谢关键酶的后续催化功能。 我们的主要兴趣和长期目标是了解 调节二氧化碳被有机物吸收的过程 这是一个对所有生物体都很常见的过程。 主要的二氧化碳同化是由核酮糖酶催化的 1，5-二磷酸（RuBP）羧化酶/加氧酶（RubisCO）。 这种蛋白质 也具有作为内部单加氧酶的功能， 在合适的条件下催化RuBP的氧解裂解。 因此，RubisCO是一种双功能蛋白，其中相同的多肽链 催化两个细胞竞争反应的第一步， 代谢;最近的研究表明，这种独特的酶可能 还作为异构酶、差向异构酶和磷酸酶发挥功能。 这 因此，研究主要针对三个方面：（1） 伴侣蛋白影响大（L）和小（S）的折叠 L/8 S/8 RubisCO的亚基;（2）RubisCO被 能够区分它的两种气态底物，二氧化碳 （3）RubisCO的活性是如何被激活的？ 在细胞中通过翻译后修饰进行调节， 额外的蛋白质。 为RubisCO建立了一个系统， 折叠研究，这将大大增强最近的结果表明， 除了已知的伴侣蛋白以外的因子的重要性。 在 此外，还开发了新的选择程序，以提高 RubisCO底物特异性研究;因此， 影响催化和底物特异性可以在一定水平上阐明 超越了有偏见的定点诱变程序。 此类研究 将很好地增强X射线和结构模型， 提供了几个RubisCO。 这些研究提供了一个很好的 将细胞代谢控制与正确折叠联系起来的机会 一个重要而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.