A Novel Fur Protein in Bradyrhizobium japonicum

Iron is an essential nutrient in almost all living organisms. However, iron can also be toxic to cells in high concentrations, and therefore organisms must maintain the proper balance of this nutrient. This project aims to understand how cells sense the availability of iron in the environment and regulate its concentration in cells. The research focuses on iron homeostasis in Bradyrhizobium japonicum, a bacterium important to agriculture and a good model for studying the metabolic regulation of gene expression. Most bacteria contain a protein called Fur, which senses and binds to iron, and regulates genes involved in iron metabolism. The model for Fur function is that binding to iron confers on the protein the ability to negatively regulate genes by recognizing specific target DNA sequences. However, the Fur protein from B. japonicum (BjFur) has unique properties that indicate novel cellular roles. In particular, BjFur binds to DNA sequences recognized by other Fur proteins, but also binds specifically to a DNA element not recognized by Fur from other bacteria. In addition, recent evidence strongly suggests that BjFur can function under iron limitation, which has not been reported in other organisms. These observations lead to the hypothesis that Fur is functionally more diverse in its activities and roles than is generally assumed. Experiments will be carried out that address the novel features of the B. japonicum Fur protein. This work will involve the training of graduate and undergraduate students, and will strongly encourage participation by women and underrepresented minority trainees.