Grant: Discovery Grants Program - Individual

Transition metals are essential for life as they are required cofactors for cell sustaining reactions such as the use of oxygen as a terminal electron acceptor by cytochrome oxidase or by ribonucleotide reductases that make the building blocks of DNA. This special reactivity of metals such as copper and iron necessitate tight control of uptake and handling by the cell to avoid toxic side effects. Understanding the mechanisms of this copper and iron homeostasis in microbes is main direction of this research program. In this proposal, systems under investigation are the iron storage protein ferritin from a pennate diatom and two systems of iron transport using a copper cofactor in bacteria. Ferritin is an iron storage protein constructed of 24 subunits that assemble into a hollow sphere. Iron is taken to the core of this nanocage by the way of ferroxidase sites where ferrous iron is converted to an iron oxide mineral and stored. In collaboration with oceanographers at UBC and the University of Washington, we show a striking example where ferritin is synthesized and used by bloom-forming pennate diatoms to store excess iron from the surrounding environment for use in subsequent cell divisions thereby out competing centric diatoms that do not possess ferritin. These bloom forming diatoms sequester carbon dioxide into the deep ocean and thus function as a key part of the carbon cycle.