One Enzyme for Two Distinct Metabolisms

描述（由申请人提供）：含硫代谢物在定义健康细胞活动的许多重要过程中发挥重要作用。为了使硫前体分子可用于随后的代谢，以及DNA和RNA代谢和各种蛋白质翻译后修饰，原核和真核细胞已经发展出挽救或保留途径。当这些途径受到损害时，就会注意到许多与健康有关的影响。例如，蛋氨酸修复途径的破坏或功能降低与癌细胞生长和肝硬化有关。此外，该途径的中间体已被证明可以影响细胞凋亡过程，而这些中间体的类似物是有希望的治疗药物，可以选择性地破坏疟疾和锥虫寄生虫的生命周期。尽管这些途径很重要，但微生物和高等生物控制其回收含硫代谢物能力的策略尚不清楚，对这些代谢物产生的各种方式也没有很好的了解。在本研究中，总体目标是更好地了解新发现和广泛传播的新型硫回收途径的机制和调控。根据最近的研究，很明显，多种生物采取的一种重要而令人惊讶的策略是利用核酮糖1,5-二磷酸羧化酶/加氧酶（RubisCO）或RubisCO样蛋白（RLP），或RubisCO和RLP两者作为锚定细胞中硫回收途径的关键反应。这两种酶都催化细胞中含硫代谢物的代谢和回收所需要的绝对必要的反应。使用一种适合遗传和生化操作的模式生物（红红螺旋菌），并采用好氧（rlp锚定）和厌氧（rubisco锚定）的甲硫氨酸/硫回收途径，我们将寻求：(a)阐明硫回收新途径所需的新反应的参与；(b)确定有氧和无氧途径是如何不同地控制的；(c)确定RubisCO的活性位点区域如何调节和催化对硫和碳代谢至关重要的反应。后一个目标提供了一个前所未有的机会，为将蛋白质结构/功能关系整合到关键和多样化的生理过程提供了新的范例。

DESCRIPTION (provided by applicant): Sulfur-containing metabolites play significant roles in many important processes that define healthy cellular activity. To make sulfur precursor molecules available for subsequent metabolism, and for DNA and RNA metabolism and various protein posttranslational modifications, prokaryotic and eukaryotic cells have developed salvage or sparing pathways. When such pathways become compromised, there are many health-related effects that are noted. For example, disruption or reduced functioning of the methionine salvage pathway has consequences relative to cancer cell growth and liver cirrhosis. In addition, intermediates of this pathway have been shown to influence apoptotic processes, while analogs of these intermediates are promising therapeutic agents that selectively disrupt the life cycle of malarial and trypanosome parasites. Despite the importance of such pathways, the strategies by which microorganisms and higher organisms control their ability to salvage sulfur-containing metabolites is not well understood, nor is there good understanding of the variety of ways in which these metabolites may be produced. In this investigation, the overall goal is to better understand the mechanism and regulation of newly discovered and wide-spread novel sulfur salvage pathways. Based on recent studies, it is apparent that an important and surprising strategy taken by diverse organisms is to employ ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) or the RubisCO-like protein (RLP), or both RubisCO and RLP, as key reactions that anchor sulfur salvage pathways in the cell. Both enzymes catalyze absolutely essential reactions that are needed for the metabolism and salvage of sulfur-containing metabolites in the cell. Using a model organism (Rhodospirillum rubrum) that is amenable to genetic and biochemical manipulation, and employs both aerobic (RLP-anchored) and anaerobic (RubisCO-anchored) methionine/sulfur salvage pathways, we will seek to: (a) elucidate the involvement of novel reactions required for new pathways of sulfur salvage; (b) determine how the aerobic and anaerobic pathways are differentially controlled; and (c) establish how the active site region of RubisCO accommodates and enables catalysis of reactions crucial to both sulfur and carbon metabolism. The latter aim presents an unprecedented opportunity to provide new paradigms for integrating protein structure/function relationships to key and diverse physiological processes.