STRUCTURE/FUNCTION OF THE E COLI H+ ATPASE

描述：现代生物学的中心问题之一是 不同形式生物能量在合成过程中的相互转化 三磷酸腺苷。在生命系统中，F1Fo-ATPase合成了大部分的ATP。他们 具有相同的基本结构和功能的线粒体，叶绿体， 和细菌。细菌ATPase，特别是大肠杆菌的酶，已经证明 是理解这些系统的结构和功能的有价值的系统 酵素。这项拟议的研究解决了质子运动的能量 与三磷酸腺苷的合成或水解有关。具体地说，能量耦合 涉及高度保守的催化β-端18%的C-末端 亚基将在包含区域的嵌合亚单位系统中进行检查 来自大肠杆菌和巨大芽孢杆菌的β亚基。这些 嵌合体显示出一种独特的能量耦合缺陷，它不会影响 ATPase活性，但确实影响ATP驱动的质子泵和 依赖呼吸的ATP合成。此缺陷是由一个或多个 比较了大肠杆菌和B。 β亚基最后75-80个残基中的巨型菌落。一种比较 牛线粒体ATPase X射线结构的这些差异 已经确定了可能影响能量耦合的残基。建议数 研究人员将把巨噬细胞序列中的那些残基突变为它们的 大肠杆菌的对应物，以确定对 能量耦合缺陷。更多的突变实验将测试 关于这些改变的氨基酸如何影响相互作用的假设 亚基内相互作用涉及在β细胞之间传递能量 亚基和伽马亚基。伽马亚单位在 跨膜Fo质子通道及其α、β亚基 ATPase。因此，这项研究的目的是阐明这条途径 质子通道与ATPase之间的能量耦合 催化点。

DESCRIPTION: One of the central problems in modern biology is the interconversion of different forms of biological energy during the synthesis of ATP. F1Fo ATPases synthesize most of the ATP in living systems. They have the same basic structure and function in mitochondria, chloroplasts, and bacteria. Bacterial ATPases, especially the E. coli enzyme, have proven to be valuable systems for understanding the structure and function of these enzymes. The proposed research addresses how the energy of proton movement is coupled to ATP synthesis or hydrolysis. Specifically, energy-coupling involving the C-terminal 18 percent of the highly-conserved catalytic beta subunit will be examined in a system of chimeric subunits containing regions of the beta subunits from both E. coli and Bacillus megaterium. These chimeras display a distinctive energy-coupling defect which does not affect ATPase activity, but does affect ATP-driven proton pumping and respiration-dependent ATP synthesis. This defect is caused by one or more of the small number of amino acid differences between E. coli and B. megaterium in the last 75-80 residues of the beta subunit. A comparison of those differences to the X-ray structure of the bovine mitochondrial ATPase has identified residues which might influence energy coupling. The proposed research will mutagenize those residues in the megaterium sequences to their E. coli counterparts to identify the residue or residues responsible for the energy coupling defect. Additional mutagenesis experiments will test hypotheses about how those altered amino acids affect inter- and intra-subunit interactions involved in transmitting energy between the beta subunit and the gamma subunit. The gamma subunit transmits energy between the transmembrane Fo proton channel and the alpha and beta subunits of the ATPase. The goal of this research, therefore, is to elucidate the pathway of energy coupling in the ATPase between the proton channel and the catalytic site.