The Mevalonate Pathway in Streptococcus

描述（由申请人提供）：肺炎链球菌（SP）每天夺去近4000人的生命，其中大多数是5岁以下的儿童。这种生物体进化出耐药性机制的能力已经产生了能够耐受我们“最后一道防线”抗生素的菌株。本实验室最近发现甲羟戊酸途径中的中间体二磷戊酸酯（DPM）是SP甲羟戊酸激酶（MK）的有效变构抑制剂，并且它不抑制人类同工酶。甲羟戊酸途径对小鼠肺组织的生存至关重要。DPM和变构位点提供了一种先导化合物和靶点，为开发一种有助于根除这种疾病的新型抗生素提供了机会。我们的初步数据表明，基于这些原理的化合物能够在富培养基中杀死感染性SP。本课题将结构、功能和合成整合在一起，旨在探索和定义SP中构成甲羟戊酸途径的三种酶，为抗生素的设计和合成提供基础。这个项目将创造的信息具有相当大的基础科学价值。构成该通路的三种酶中的每一种都是GHMP激酶蛋白超家族的成员，其生物医学相关性延伸到孤儿疾病和白内障形成。我们已经从SP中确定了MK的结构，并且与结合底物的dpm抑制复合物的结构即将到来。这些结构定义了mk靶标，并将揭示DPM结合如何破坏化学。我们还从SP中确定了磷酸戊酸激酶（PMK）的三元复合物的结构，这提出了有趣的机制问题，强调了PMK的独特和家族结构元素。二磷戊酸脱羧酶（DPM- dc）是一种通过碳正离子过渡态使DPM脱羧的酶。我们将通过定义其过渡态结构和监测配体和中间配合物的形成来探索DPM-DC机制，为这类机制创建一个先进的催化范例。

DESCRIPTION (provided by applicant): Streptococcus pneumonia (SP) takes the lives of nearly 4000 people daily, the majority of whom are children below the age of five. The organism's ability to evolve resistance mechanisms has produced strains capable of tolerating our "last line of defense" antibiotics. This laboratory recently discovered that diphosphomevalonate (DPM), an intermediate in the mevalonate pathway, is a potent allosteric inhibitor of the SP mevalonate kinase (MK), and that it does not inhibit the human isozyme. The mevalonate pathway is essential for survival of the organism in mouse lung. DPM and the allosteric site offer a lead compound and target that provide an opportunity to develop a new class of antibiotics that could help eradicate this disease. Our preliminary data demonstrate that compounds based on these principles are capable of killing infectious SP in rich media. This proposal integrates structure, function and synthesis in a project designed to explore and define the three enzymes that comprise the mevalonate pathway in SP, and, in so doing, provide a basis for the design and synthesis of antibiotics. The information that this program will create is of considerable fundamental scientific value. Each of the three enzymes that comprise the pathway is a member of the GHMP kinase protein superfamily, whose biomedical relevance extends to both orphan diseases and cataract formation. We have determined the structure of MK from SP, and the structure of the DPM-inhibited complex with bound substrates is imminent. These structures define the MK-target and will reveal how DPM binding disrupts chemistry. We've also determined the structure of a ternary complex of phosphomevalonate kinase (PMK) from SP, which raises intriguing mechanistic issues that emphasize both the unique and familial structural elements of PMK. Diphosphomevalonate decaboxylase (DPM-DC) is a fascinating enzyme that decarboxylates DPM via a carbocationic transition-state. We will explore the DPM-DC mechanism by defining its transition-state structures and monitoring the formation of ligand and intermediate complexes to create an advanced catalytic paradigm for this mechanistic class.