Localization and Characterization of the Fe(II) Oxidase Complex from Rhodopseudomonas palustris TIE-1

以亚铁为基础的光合作用[Fe(II)]被认为是地球历史早期的一个重要过程，但在分子水平上对这种新陈代谢了解很少。如果我们要在岩石记录中追踪这种新陈代谢的起源(如古代沉积沉积物中所记录的带状铁地层)，了解哪些生物分子催化了这一过程以及它们是如何工作的，这将是至关重要的。考虑到这一目标，PI的实验室分离出了一种遗传上易驯化的沼泽红假单胞菌(Tie-1)菌株，这是一种革兰氏阴性、产氧的光生细菌，作为研究这种新陈代谢的模型系统。最近，有三个基因被鉴定为光营养铁氧化的必需基因：pioA、pioB和pioc。本项目的目标是探索这些基因产物的生物化学，具体有三个目标：1)研究Pio蛋白的定位。推测PioA和Pioc位于周质间隙，而PioB位于外膜。2)鉴定Pio蛋白的功能。该项目将检验这样的假设，即PioA直接结合和氧化Fe(II)，而PioC将电子从PioA运送到细胞质内膜的电子传输链。此外，该项目将测试PioB是否与PioA相互作用，和/或PioB是否参与Fe(II)的运输。3)解决与Fe(II)直接结合和氧化的蛋白质的晶体结构。推测该蛋白为PioA。更广泛的影响这个项目将在博士后和本科生水平上实现分子地球生物学的高级培训。除了对学生进行直接培训外，该项目还将支持社区外展活动，包括向少数群体听众和普通公众发表公开演讲。最后，为了补充这一项目，国际和平研究所将向美国微生物学会申请美国国家科学基金会国际旅行奖和/或国际教授职位，以支持继续与委内瑞拉的一位同事开展现有的合作。

Photosynthesis based on ferrous iron [Fe(II)] is thought to have been an important process early in Earth history, yet very little is understood about this metabolism at the molecular level. If we are ever to trace the origin of this metabolism in the rock record (as recorded in ancient sedimentary deposits known as Banded Iron Formations), it will be essential to understand which biomolecules catalyze this process and how they work. With this goal in mind, the PI's laboratory isolated a genetically-tractable strain of Rhodopseudomonas palustris (TIE-1), a Gram-negative, anoxygenic phototroph to serve as a model system to study this metabolism. Recently, three genes were identified as essential for phototrophic iron oxidation: pioA, pioB and pioC. The goal of this project is to explore the biochemistry of the products of these genes, with three specific objectives: 1) To study the localization of the Pio proteins. It is hypothesized that PioA and PioC reside in the periplasmic space, whereas PioB resides in the outermembrane. 2) To characterize the functions of the Pio proteins. The project will test the hypothesis that PioA directly binds and oxidizes Fe(II), whereas PioC carries electrons from PioA to the electron transport chain in the intra cytoplasmic membrane. In addition, the project will test if PioB interacts with PioA, and/or if PioB is involved in Fe(II) transport. 3) To solve the crystal structure of whichever protein proves to be the one that directly binds and oxidizes Fe(II). It is postulated that this protein is PioA. Broader ImpactsThis project will enable the advanced training in molecular geobiology at postdoctoral and undergraduate student level. Beyond the direct training of students, this project will support community outreach activities including public speaking to minority audiences and the general public. Lastly, to complement this project, the PI will apply for an NSF-International travel award and/or an International Professorship from the American Society for Microbiology to support the continuation of an existing collaboration with a colleague in Venezuela.