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

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

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 Impacts This 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.