BIOENERGETICS AND PROTON PUMPS IN MALARIA PARASITES

超出所提供的空间。跨质膜运输是所有细胞生理学的一个关键特征。许多在质膜上的看门人是由离子和电梯度在膜上辅助的。为了维持这种电化学梯度，细胞消耗了巨大的能量——高达细胞内ATP的50%。在疟疾寄生虫中，用电化学梯度给质膜充电以进行这种运输的能量经济学几乎是未知的。疟疾寄生虫的红细胞阶段主要通过底物水平的磷酸化获得ATP，每个葡萄糖分子只有两个ATP分子，这一事实必然对寄生虫的能量利用产生重大限制。该项目旨在探索疟疾寄生虫的替代和/或辅助能源。最近的证据表明，疟原虫含有两个成员（PfVP1和PfVP2）的植物样的能量保存，膜相关的H*泵送焦磷酸酶。植物的空泡焦磷酸酶（V-PPases）将无机焦磷酸盐（PP_）的磷酸酐键水解产生的能量偶联，泵送H¿穿过空泡膜。在疟疾寄生虫中，初步数据表明这种酶位于寄生虫的质膜内。这一位置表明，通过pp酶的PP_水解和v型ATP酶的ATP水解，H¿在寄生虫质膜上的易位可以被激活。由于动物细胞不具有v - ppase的同源物，这些酶在疟疾寄生虫中的存在为设计选择性毒性抑制剂提供了候选物。本项目将对PfVP1和PfVP2的生物化学和细胞生物学进行基础研究。将采用基因破坏方法来评估这些分子对寄生虫生理的贡献。探讨疟原虫v -ATP酶在高能量需求下利用V-PPases产生的质子动力反向作用合成ATP的可能性。此外，研究人员还将研究疟原虫FoF1-ATP合成酶的一个不寻常的亚基结构，以评估这种线粒体质子泵送复合体对寄生虫生理的贡献。这个项目的结果有可能要求我们对疟疾寄生虫生物能量学的观点进行重大修订。该项目可能揭示疟疾寄生虫中质子稳态和生物能量学的独特特征，为设计新的疟疾控制方法奠定基础。PERFORMANCESITE ( ======================================== 节结束 ===========================================

EXCEED THE SPACE PROVIDED. Transport across the plasma membrane is a critical feature of all cellular physiology. Many gatekeepers at the plasma membrane are assisted by ionic and electric gradients across the membrane. Cells expend enormous energy-- up to 50% of intracellular ATP-- for maintenance of such electrochemical gradients. Energy economics of charging the plasma membrane with an electrochemical gradient for such transport remains virtually unknown in malaria parasites. The fact that erythrocytic stages of malaria parasites derive their ATP mainly through substrate-level phosphorylation, eking out a mere two ATP molecules per glucose molecule, must place significant constraints on parasite energy utilization. This project seeks to explore an alternate and/or adjunct energy source for malaria parasites. Recent evidence shows that Plasmodium species contains two members (PfVP1 and PfVP2) of the plant-like energy- conserving, membrane-associated H*-pumping pyrophosphatases. The vacuolar pyrophosphatases (V-PPases) of plants couple the energy generated by hydrolysis of the phosphoanhydride bond of inorganic pyrophosphate (PP_) to pump H ¿ across the vacuolar membrane. In malaria parasites, preliminary data suggest that the enzyme is located within the parasite plasma membrane. This location would suggest that H¿ translocation across the parasite plasma membrane could be energized through PP_ hydrolysis by the PPases in concert with ATP hydrolysis by the V-type ATPase. Because animal cells do not possess homologues of V-PPases, the presence of these enzymes in malaria parasites offers candidates for devising selectively toxic inhibitors. This project will undertake basic investigations on the biochemistry and cell biology of PfVP1 and PfVP2. Gene disruption approaches will be undertaken to assess contributions made by these molecules to the parasite physiology. The possibility that V-ATPase of malaria parasites may function work in reverse to synthesize ATP by using the proton motive force generated by the V-PPases under high energy demand will be explored. Furthermore, an unusual subunit configuration observed for the FoF1-ATP synthase of malaria parasites will be investigated to assess the contribution of this usually mitochondrial proton pumping complex to parasite physiology. Results from this project have a potential to require a major revision of our view of malaria parasite bioenergetics. Unique features of proton homeostasis and bioenergetics in malaria parasites likely to be uncovered in this project could form the basis for devising novel approaches to malaria control. PERFORMANCESITE( ========================================Section End===========================================